Biopolymers Information

BIOTECH SUPPORT SERVICES (BSS), INDIA
2014
BIOPOLYMERS
S. N. JOGDAND
4 0 8 A R C H A N A B U I L D I N G , S E C T O R 1 7 , V A S H I , N A V I M U M B A I , I N D I A

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BIOPOLYMERS
CONTENTS
Chapter No. Contents Page No.
1 Introduction to Biopolymers 3
2 Biogums (Biopolysaccharides) 21
3 Biosurfactants and Bioemulsifiers 58
4 Bioflocculants 85
5 Bioadhesive (Protein Biopolymer) 100
6 Biodetergents and Biolubricants 108
7 Chitin and Chitosan 111
8 Pectin 126
9 Microbial Cellulose 132
10 Lignin 153
11 Polyamides 158

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CHAPTER 1
INTRODUCTION TO BIOPOLYMERS
1.1 Introduction
1.2 Biopolymers Vs Synthetic Polymers
1.3 Why Biopolymers are interesting?
1.4 Biodegradable Polymers
(I) Natural Polymers
(II) Synthetic Polymers
1.5 Members of Biopolymer Family
1.6 Market for Biopolymers
1.7 Factors affecting Biopolymer Market
1.8 Factors affecting Biopolymer production
1.9 Biotechnological Production of Biopolymers
1.10 Purification and Determination of Biopolymers
1.11 Working Document of EuropaBio
1.12 Biopolymers in Construction Engineering
1.13 Problems Associated with Biopolymers
1.14 Additives for Biopolymers
1.1 Introduction
A recent report (C&News, 2009) estimates over $100 billion of the current global
chemicals market. About 3% (i.e., €51bn-77bn ($61bn-93bn)) are derived from either
bio-based feedstock or fermentation or enzymatic conversion or combination of them.
This report projected that the share of bio-derived chemicals would grow to about 15% of
global chemical sales by 2025.
The field of biopolymers, while still in its early stages, is growing in popularity everyday.
For most biopolymers, it's still too early to determine if they'll be economically feasible on
a large, industrial scale. The advent of biopolymers has revolutionized polymer science.
Derived from natural sources, these biodegradable, biocompatible and usually nontoxic
polymers, are well received, owing to their unique set of properties that make them
favorite for use in wide areas of industrial as well as medical applications.
Biopolymers such as the Polyhydroxyalkanoates (PHAs) and the Exopolysaccharides
(EPS) are diverse and versatile class of the materials that have potential applications in
virtually all sectors of the economy.
1.2 Biopolymers Vs Synthetic Polymers
Both polymers as well as biopolymers have repetitive units called as monomers. While
synthetic polymers have much simpler and random structures, biopolymers have more
complex structure developed out of primary, secondary and tertiary stages. Biopolymers
of a particular type contain the same sequence and number of monomers and thus all
have the same mass. Phenomenon is called as monodispersity while synthetic polymers
show polydispersity. So biopolymers have polydispersity index of 1. Biopolymers are
created by living cells. Biopolymers may be produced using renewable resources in
nature.
Biopolymers have diversity in structure and have unique properties which make them
useful in food, pharmaceutical and industrial applications. Biomaterials are getting
increased importance today as they are the part of living organisms and provide
structure, function, protection and storage products available with their use.
1.3 Why Biopolymers are interesting?

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Biopolymers are interesting for us because –
(i) They possess unique properties which can not be emulated by synthetic polymers.
(ii) They are available from renewable resources.
(iii) They are biodegradable (hence ecofriendly).
Biopolymers are finding increasing applications as bioplastic, biosurfactant,
biodetergent, bioflocculant, biodegradable polyesters, biogums etc. Research and
applications in the field of biomaterial is an ever expanding field today.
They can modify the flow characteristics of fluids, stabilize suspensions, flocculate
particles, encapsulate materials and produce emulsions. Consequently, they are now
widely used as thickener, stabilizer, emulsifier, gelling agent and water-binding agents in
the food, cosmetics, bioplastics and oil industries. Moreover, some polysaccharides
have unique physiological activities as anti-tumour, anti-viral and anti-inflammatory
agents as well as an inducer for interferon, platelet aggregation inhibition and colony
stimulating factor synthesis.
Biodegradable polymers can be processed into useful plastic materials and used to
supplement blends of the synthetic and microbial polymer. Among the polysaccharides,
cellulose and starch have been the most extensively used. Cellulose represents an
appreciable fraction of the waste products. The main source of cellulose is wood, but it
can also be obtained from agricultural resources. Cellulose is used worldwide in the
paper industry, and as a raw material to prepare a large variety of cellulose derivatives.
Among all the cellulose derivatives, esters and ethers are the most important, mainly
cellulose acetate, this is the most abundantly produced cellulose ester. They are usually
applied as films (packaging), fibers (textile fibers, cigarette filters), and plastic molding
compounds. Citric esters (triethyl and acetyl triethyl acetate) were recently introduced as
biodegradable plasticizers in order to improve the rheological response of cellulose
acetate.
The most-used biopolymers are natural rubber (used since the mid-1700s), cellulosics
(invented in the late-1800s), and nylon 11 and 6–10 (mid-1900s). Newer biopolymers
include polylactic acid (PLA) and polyhydroxyalkanoate (PHA) from corn, bio-based
thermoplastic polyurethanes (TPU), and epoxy from the biodiesel byproduct glycerol.
One recent development is polyethylene (PE) and polypropylene (PP) made from sugar
cane in Brazil. However, the problems that farmers have always faced, such as drought,
pests and extreme weather, have limited availability of these products and caused
seasonal price fluctuations.
1.4 Biodegradable Polymers
(I) Natural Polymers
i. Polysaccharides – Starch, Cellulose
ii. Proteins – Gelatin, Casein, Silk, Wool, Collagen
iii. Polyesters – Polyhydroxyalkonates
iv. Others – Lignin, Shellac, Natural Ruber
(II) Synthetic Polymers
i. Polyalkylene esters
ii. Polylatic acid and its copolymers
iii. Polyamide esters
iv. Polyvinyl esters
v. Polyvinyl alcohol
vi. Polyanhydrides

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1.5 Members of Biopolymer Family
No. Biopolymer Group Examples
1 Polyesters Polyhydroxyalkonates, Polylactic acid
2
Polysaccharides
(plant/algal)
Starch (amylose/amylopectin)
Cellulose, Agar, Alginate, Carrageenan, Pectin,
Konjac, Various gums (e.g., guar)
3
Polysaccharides
(bacterial)
Xanthan, Dextran, GelIan, Levan, CurdIan,
Polygalactosamine, Cellulose (bacterial)
4
Polysaccharides
(animal)
Chitin/chitosan, Hyaluronic acid
5
Polysaccharides
(fungal)
Pullulan, Elsinan, Yeast glucans
6 Proteins
Silks, Collagen/gelatin, Elastin, Resilin, Adhesives,
Polyamino acids, Soy, zein, wheat gluten, casein,
Serum albumin
7 Lipids/ Surfactants
Acetoglycerides, waxes, surfactants
Emulsan
8 Polyphenols Lignin, Tannin, Humic acid
9 Specialty polymers
Shellac, Poly-gamma-glutamic acid, Natural rubber,
Synthetic polymers from natural fats and oils
(e.g.,nylon from castor oil)
Sr. No. Class of Biopolymer by Application Examples
1 Bioplastic
Polyhydroxy alkonates, Polylactic
Acid
2 Biosurfacant
3 Biodetergent
4 Bioadhesive
5 Bioflocculant
As was pointed out above, the processing and in-use biopolymer properties depend on
the addition of other materials that provide a more convenient processing regime and
stabilizing effects. Therefore the identification and further determination of these
additives, as well as the separation from the biopolymer matrix, is necessary, and
chromatographic techniques are a powerful tool to achieve this goal.
Biopolymers are polymers that occur in nature.
 Cellulose is the most plentiful carbohydrate in the world; 40 percent of all
organic matter is cellulose!
 Starch is found in corn (maize), potatoes, wheat, tapioca (cassava), and some
other plants. Annual world production of starch is well over 70 billion pounds, with
much of it being used for non-food purposes, like making paper, cardboard,
textile sizing, and adhesives. Starch is an enormous source of biomass and most

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applications are based on this natural polymer. It has a semi-crystalline structure
in which their native granules are either destroyed or reorganized. Water and,
recently, low-molecular-weight polyols, are frequently used to produce
thermoplastic starches. Starch can be directly used as a biodegradable plastic for
film production because of the increasing prices and decreasing availability of
conventional film-forming materials. Starch can be incorporated into plastics as
thermoplastic starch or in its granular form. Recently, starch has been used in
various formulations based on biodegradable synthetic polymers in order to
obtain totally biodegradable materials. Thermoplastic and granular starch was
blended with polycaprolactone (PCL), polyvinyl alcohol and its co polymers, and
polyhydroxyalcanoates (PHAs). Many of these materials are commercially
available, e.g., Ecostar (polyethylene/starch/unsaturated fatty acids), Mater Bi Z
(PCL / starch/natural additives) and Mater Bi Y (polyvinylalchol-co-
ethylene/starch/natural additives). Natural additives are mainly polyols.
 The proteins, which have found many applications, are, for the most part,
neither soluble nor fusible without degradation. Therefore, they are used in the
form in which they are found in nature. Gelatin, an animal protein, is a water-
soluble and biodegradable polymer that is extensively used in industrial,
pharmaceutical, and biomedical applications. A method to develop flexible gelatin
films is by adding polyglycerols. Quite recently, gelatin was blended with
poly(vinyl alcohol) and sugar cane bagasse in order to obtain films that can
undergo biodegradation in soil. The results demonstrated the potential use of
such films as self-fertilizing mulches.
 Collagen is the most abundant protein found in mammals. Gelatin is denatured
collagen, and is used in sausage casings, capsules for drugs and vitamin
preparations, and other miscellaneous industrial applications including
photography.
 Casein, commercially produced mainly from cow's skimmed milk, is used in
adhesives, binders, protective coatings, and other products.
 Soy protein and zein (from corn) are abundant plant proteins. They are used for
making adhesives and coatings for paper and cardboard.
 Polyesters are produced by bacteria, and can be made commercially on large
scales through fermentation processes. They are now being used in biomedical
applications.
These natural raw materials are abundant, renewable, and biodegradable, making them
attractive feedstocks for bioplastics, a new generation of environmentally friendly
plastics.
 Starch-based bioplastics are important not only because starch is the least
expensive biopolymer but because it can be processed by all of the methods
used for synthetic polymers, like film extrusion and injection moulding. Eating
utensils, plates, cups and other products have been made with starch-based
plastics.
 Interest in soybeans has been revived, recalling Ford's early efforts. In research
laboratories it has been shown that soy protein, with and without cellulose
extenders, can be processed with modern extrusion and injection moulding
methods.
 Many water soluble biopolymers such as starch, gelatin, soy protein, and casein
form flexible films when properly plasticized. Although such films are regarded
mainly as food coatings, it is recognized that they have potential use as
nonsupported stand-alone sheeting for food packaging and other purposes.

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 Starch-protein compositions have the interesting characteristic of meeting
nutritional requirements for farm animals. Hog feed, for example, is
recommended to contain 13-24% protein, complemented with starch. If starch-
protein plastics were commercialized, used food containers and serviceware
collected from fast food restaurants could be pasteurized and turned into animal
feed.
 Polyesters are now produced from natural resources-like starch and sugars-
through large-scale fermentation processes, and used to manufacture water-
resistant bottles, eating utensils, and other products.
 Lactic acid is now commercially produced on large scales through the
fermentation of sugar feedstocks obtained from sugar beets or sugar cane, or
from the conversion of starch from corn, potato peels, or other starch source. It
can be polymerized to produce poly(lactic acid), which is already finding
commercial applications in drug encapsulation and biodegradable medical
devices.
Poly(lactic acid) has become a significant commercial polymer. Its clarity makes
it useful for recyclable and biodegradable packaging, such as bottles, yogurt
cups, and candy wrappers. It has also been used for food service ware, lawn and
food waste bags, coatings for paper and cardboard, and fibers-for clothing,
carpets, sheets and towels, and wall coverings. In biomedical applications, it is
used for sutures, prosthetic materials, and materials for drug delivery.
 Triglycerides have recently become the basis for a new family of sturdy
composites. With glass fiber reinforcement they can be made into long-lasting
durable materials with applications in the manufacture of agricultural equipment,
the automotive industry, construction, and other areas. Fibers other than glass
can also be used in the process, like fibers from jute, hemp, flax, wood, and even
straw or hay. If straw could replace wood in composites now used in the
construction industry, it would provide a new use for an abundant, rapidly
renewable agricultural commodity and at the same time conserve less rapidly
renewable wood fiber.
Triglycerides can also be polymerized. Triglycerides make up a large part of the
storage lipids in animal and plant cells. Over sixteen billion pounds of vegetable
oils are produced in the United States each year, mainly from soybean, flax, and
rapeseed. Triglycerides are another promising raw material for producing
plastics.
 Other kinds of natural polymers, which are produced by a wide variety of bacteria
as intracellular reserve material, are receiving increasing scientific and industrial
attention, for possible applications as melt processable polymers. The members
of this family of thermoplastic biopolymers are the PHAs. Poly (3-hydroxy)
butyrate (PHB), and poly (3-hydroxy) butyrate-hydroxyvalerate (PHBV)
copolymers, which are microbial polyesters exhibiting useful mechanical
properties, present the advantages of biodegradability and biocompatibility over
other thermoplastics. Poly (3-hydroxy) butyrate has been blended with a variety
of low- and high-cost polymers in order to apply PHB-based blends in packaging
materials or agricultural foils. Blends with nonbiodegradable polymers, including
PVAc, PVC, and PMMA, are reported in the literature. Poly(3-hydroxy)butyrate
has been also blended with synthetic biodegradable polyesters, such as
poly(lactic acid) (PLA), poly(caprolactone), and natural polymers including
cellulose and starch.

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The widespread use of these new plastics will depend on developing technologies and
society‘s commitment to the concepts of resource conservation, environmental
preservation, and sustainable technologies. There are growing signs that people indeed
want to live in greater harmony with nature and bioplastics are expected to become
important.
Depending to the evolution of the synthesis process, different classifications of the
different biodegradable polymers have been proposed. Figure 1 shows an attempt at
classification. We have 4 different categories. Only 3 categories (1 to 3) are obtained
from renewable resources:
1. Polymers from biomass such as the agro-polymers from agro-resources (e.g., starch,
cellulose),
2. Polymers obtained by microbial production, e.g., the polyhydroxy-alkanoates,
3. Polymers conventionally and chemically synthesised and whose the monomers are
obtained from agro-resources, e.g., the poly (lactic acid),
4. Polymers whose monomers and polymers are obtained conventionally, by chemical
synthesis.
We can also classify these different biodegradable polymers into two main families: the
agro-polymers (category 1) and the biodegradable polyesters (categories 2 to 4).
1.6 Market for Biopolymers
A recent survey conducted shows that global demand would grow from 180 million tons
to 258 million tons by 2010 - definitely growing faster than the commonly used plastics
such as polyolefins. Toyota expects that the demand would reach almost 5% of the total
petrochemical based polymer demand in the World by 2020. High growth scenarios are
predicting European production of up to 800 kton in 2010 and even 3,000 kton in 2020.
Between 1999 and 2004, the worldwide production capacity for biopolymers grew
significantly, to about 250 000 tonne/year. The rise in capacity clearly shows how they
are emerging from being a niche market and moving to mass production scale.
Within Europe, recent figures indicate that consumption has increased from 20 000
tonne in 2001 to 50 000 tonne in 2004. By 2015, this consumption is expected to
increase to about 1m tonne. Moreover, the long-term substitution potential of
biopolymers is estimated at up to 15m tonne within the EU, a capacity that would meet
about one-third of present plastic production.
In 2007 the total estimated global production for all biopolymers was approximately
280M lb. The total 2010–2012 capacity planned in Brazil for PE/PP biopolymers is 740M
lb/yr, but the estimated total US production of conventional PE/PP in 2007 was a much
greater 60B lb. Thus, the present and planned production worldwide of all biopolymers
equals only 0.017% of US PE/PP production. Consequently, it seems highly unlikely that
biopolymers will ever be more than specialty materials.
1.7 Factors affecting Biopolymer Market
1. Soaring oil prices,
2. Depleting oil reserves,
3. Worldwide interest in renewable resources,
4. Growing concern regarding greenhouse gas emissions and
5. A new emphasis on waste management
6. Total Life Cycle Assessment,
7. Legislative incentives (particularly in European Union),
8. Suitability of material properties,
9. Technical feasibility of processing options, and
10. Commercial viability of production and processing.

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11. Consumer Acceptance
12. Range of Applications
The use of legislative instruments is a significant driver influencing the adoption of
biopolymers in place of the petroleum based polymers. In Europe and Japan, the
automotive and packaging sectors are most affected by ratified legislation. The
Packaging and Packaging Waste Directive 94/62/EC and the End of Life Vehicle
Directive 2000/53/EC are two examples of such legislative drivers. Additionally, in the
U.S. Section 9002 of the Farm Security and Rural Investment Act of 2002 confers
federal purchasing preference to biopolymer based products.
New technologies in plant breeding and processing are narrowing the biopolymers-
synthetic plastics cost differential, as well as improving material properties.
Implementation of the Kyoto Protocol will also bring into sharper focus the relative
performance of biopolymers and synthetics in terms of their respective energy use and
CO 2 emissions. (Under the Kyoto Protocol, the European Community agreed to reduce
emissions from 1990 levels by 8% during the period 2008 to 2012 and Japan has
similarly agreed to reduce emissions by 6%). As a rule of thumb, starch-based plastics
can save between 0.8 and 3.2 tons of CO2 per ton compared to one ton of fossil fuel-
derived plastic, the range reflecting the share of petroleum based copolymers used in
plastics.
Natureworks has doubled its capacity and produced 200 million pounds in 2010.
NatureWorks‘ PHA biopolymers are used in more than 20 commercial applications that
are available at 70,000 retail sites. NatureWorks — based in Minnetonka, Minn., with a
300 million pound-capacity plant making Ingeo-brand PLA in Blair, Neb. — is exploring
ways to use all-natural cellulose as a feedstock. Far less than 1% of food is used for
production of biopolymers.
Telles has opened its 110-million-pound-capacity plant making PHA biopolymers in
Clinton, Iowa. Four commercial grades of Telles‘ Mirel-brand PHA now are available,
including ones for injection molding, thermoforming, cast sheet and cast/blown film.
Lowell, Mass.-based firm is a joint venture between technology provider Metabolix Inc.
and agricultural leader Archer Daniels Midland. Cereplast — based in El Segundo, Calif.
— recently opened an 80-million-pound-capacity plant in Seymour, Ind., making its
Compostables and Hybrid lines of biopolymer materials.
Consumer acceptance of compostable packaging is a bigger barrier than the actual
supply of material, according to some American Biopolymer Manufacturers. Another
concern is that it is considered that biopolymers are taking land away from food
production. This is a misconception and there is ample of land available for growing
crops for biopolymers. Growing crops for biofuels or biopolymers is really not a
competition.
Due to their diversity in structure and unique properties, they have a wide range of food,
pharmaceutical, and industrial applications.
1.8 Factors Affecting Biopolymers Production
Biopolymers potentially have an important role in shaping the future of the personal
hygiene/grooming, cosmetics, medical implant/devices, textile, and food sectors, but are
not substitutes for the conventional polymers that dictate our current way of living.
Today‟s Capacity: The total capacity for biopolymers in 2009 was around 500 million
lbs. These include polylactide acid [PLA] (NatureWorks, Galactic, Hycail BV);
polyhydroxyalkanoates such as PHAs, PHB, and PHBH (Biomer, Procter&Gamble);
polymers based on bio-based PDO (DuPont); cellulose polymers (Innovia Films); epoxy
polymers from bio-glycerol; and starch polymers and blends (AkzoNobel [National
Starch Chemical] and several other players). NatureWorks (Cargill Dow) is the major

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commercial player with a PLA capacity of 280 million lbs; and Novamont is the major
producer of starch polymers and blends, with a capacity of 120 million lbs.
The total capacity of biopolymers is expected to reach 1.3 billion lbs, if Braskem's 400
million lbs/year of bio-polyethylene production and Braskem's/Nova Zymes's 400 million
lbs/year of bio-polypropylene production materializes in Brazil. At these levels, the
biopolymer's share of the total global production of synthetic polymers will be a meager
0.26%.
 If biopolymers were to replace all of the polymer products, the amount of
biopolymer production would need to increase nearly 400-fold (from 1.3 billion lbs
to over 520 billion lbs). This would undoubtedly put a strain on our planet's
ecosystem and require massive deforestation.
 Plant-based biopolymers are based on green sources and typically cost more in
energy and processing than conventional polymers. Government subsidies, tax
credits, and other incentives provided to farmers and end-users further obscures
the real cost of production. Although PLA was known as the first commercially
available synthetic "biodegradable" polymer, it is now recognized as a
"compostable" polymer (heat and moisture are needed to degrade it). In addition,
infrared sensor devices are required to sort out PLA from other wastes. The
portion of biopolymer waste in landfills is infinitesimal. Having waste
management try to find biopolymer waste from a colossal pile of garbage is like
finding a needle in a haystack. The current amount of plastics, glass, and paper
that is recycled is small and most of these used products end up in landfills. One
can expect the same trend for biopolymer wastes, and given that they would not
undergo total biodegradation without heat and moisture, these products would
also contribute to creating more landfills.
 Until a truly biodegradable product is developed, governments will need to
improve public awareness and increase efforts for recycling/appropriate
waste management from its current state. Germany has taken a lead towards
this effort.
 PLA and other biopolymers compete with bio-ethyl acetate and other bio fuels
such as bio-ethanol and bio-diesel, which are also made from the same natural
sources of corn, sugarcane, etc. These sources are the backbone of our food
industry. Even if biopolymer production currently contributes only minimally
towards food scarcity and its increase in costs, the potential to eventually further
limit lands for food production will continue to raise public debate.
 Cultivation of land for biopolymers makes the land unavailable for other food
crops, forcing the need for deforestation.
 Another issue is that bio-products, like food products, are at the mercy of
Mother Nature.
 Just as floods, droughts, and unpredictable seasonal variations can impact the
supply of crops for food, these environmental factors could impact the stability
of biopolymer production as well.
 Finally, the environmental costs to convert marginal land into a fertile farm for
production of corn or sugarcane is excessive, and involves the use of large
amounts of agricultural machines (tractors, harvesters, tillage equipment,
grinders, choppers, etc.) which are based on diesel, fuel, and gas. In addition,
expensive chemical fertilizers are used to increase the harvest yield and
frequency of harvests each year.The use of diesel, fuel, and gas will create more
greenhouse gases; and the use of chemical fertilizers will reduce the organic
matter of soil, further contributing to greenhouse gas emissions.

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Bio- and food products competing for the same resources and politically driven green
initiatives have distorted intrinsic potential for biopolymers.
1.9 Biotechnological Production of Biopolymers
Biopolymers can be obtained from plant, animal, marine, and microbial sources. A huge
variety of biopolymers, such as polysaccharides, polyesters, and polyamides, are
naturally produced by microorganisms. Nowadays, microbial biopolymers are considered
as important sources of polymeric materials that have a great potential for
commercialization. They can modify the flow characteristics of fluids, stabilize
suspensions, flocculate particles, encapsulate materials and produce emulsions.
Consequently, they are now widely used as thickener, stabilizer, emulsifier, gelling agent
and water-binding agents in the food, cosmetics, bioplastics and oil industries. Moreover,
some polysaccharides have unique physiological activities as anti-tumour, anti-viral and
anti-inflammatory agents as well as an inducer for interferon, platelet aggregation
inhibition and colony stimulating factor synthesis. Properties of biopolymers are
dependent on the composition and molecular weight of the polymer. The genetic
manipulation of microorganisms opens up an enormous potential for the biotechnological
production of biopolymers with tailored properties suitable for high-value medical
application such as tissue engineering and drug delivery.
The production of biopolymers using microorganisms typically requires five times as
much water to separate the biopolymer from the biocatalyst than is required for
conventional chemical processes. This means that more energy and much higher water
processing capacity are needed; creating an environmental impact that goes well
beyond simple cost considerations.
Biopolymers production in 2000 was more than 25kton. High growth scenarios are
predicting European production of biopolymers up to 800 kton in 2010 and even 3,000
kton in 2020.
In the industrial sector, biopolymers, also widely known as bioplastics, hold applications
chiefly in market sectors such as packaging, electronics, automotive and agriculture.
Bioplastics have the largest application in the packaging industry with other sectors such
as electronics, automotive and agriculture growing to meet the demands for
environment-friendly products.
In the medical field, biopolymers are a new and exciting area of research and incite
tremendous optimism to be employed in three main end-sector applications, namely the
medical devices, tissue engineering and the drug delivery market. Therefore,
biopolymers hold a remarkably diverse scope of applications, which is bound to grow in
the coming decades.
The use of biopolymers has evolved from employing them in simple medical devices
such as tissue adhesive surgical patches, meshes, tissue screws and tacks, dental
implants, contact lenses, tissue adhesives, sealants and wound closing sutures to
employing them today in complex devices such as orthopedic fixation products,
cardiovascular stents and heart valves.
1.10 Purification and Determination of Biopolymers
The amount of biopolymer was purified from different cultures broth by the method
described by Yun & Park. The culture broth (after diluted with distilled water as needed)
was centrifuged at 14000 rpm for 30 min, to remove the cells. The biopolymer in the
supernatant was harvested by acetone precipitation (1 culture: 3 acetone) and
centrifugation. The sediment was washed with 70% ethanol and re-dissolved in distilled
water. The biopolymer was further purified by cetyl-trimethyl-ammonium bromide (1:1)
precipitation followed by ethanol precipitation in 10 % NaCl solution. After washing with

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70 % ethanol, the precipitated biopolymer was lyophilized to obtain a purified biopolymer
fraction then weighed and expressed as dry weight (g) per liter of culture broth.
1.11 Working Document of EuropaBio
Working Document of EuropaBio on Industrial Biotechnology describes –
Advanced Biopolymers
Biological molecules have rich physico-chemical behaviour, mostly due to the
abundance of functional groups at close proximity which allow for a variety of directional
and random interactions. Advanced biopolymeric materials will satisfy new (improved)
properties, extension of applications (durability: service life, recyclability) etc. Although
many of the needs are known and expressed by industry it is foreseen that many of
these developments will take up to 10 years to emerge fully commercial (mid/long term).
- Monodisperse oligomers/polymers
- Chiral oligomers/polymers (for coatings/pigments)
- Liquid crystal character
- Block-copolymers and other new polymers
- New building blocks (high T, high mechanical properties, high flow)
- Optical clearance and dimensional precision
Bio-inspired materials
Scientific and technological developments create new opportunities (application
possibilities and needs / new markets) Developments in this area are typically long term
(> 10 years). In this case, nature serves as an inspiration for entirely novel structures as
well as new manufacturing processes.
- Electronics, e.g. solar cell efficiency needs controlled transport phenomena,
attainable through fractal structures
- Bio-structures: protein crystals & inorganic structures (e.g. bones, shells)
- Dimension stability, miniaturised structures and devices
- Surface structuring on very small scales (e.g. data storage)
- Barrier properties
- Chemical / physical sensing (e.g. smart packaging, personal identification, etc.).
- Interference colouring / multi thin layer structuring (pearlescence of chitine)
 Bio-materials as healing dressings and/or scaffolds in tissue engineering.
Some bio-materials such as bacterial cellulose or chitosan are known as healing
dressings. However, the wound healing process can be increased or accelerated
by simultaneous application of bio-active compounds (nucleotides, oligopeptides
and some lysophospholipids) which can act as ligands for cell surface-bound
receptors involved in signal transduction. The binding of such compounds (or
ligands) to these receptors can stimulate the proliferation of keratinocytes,
fibroblasts, endothelial cells and other cell types which are involved in the wound
healing process.
Research should be focused on the use of bio-materials as carriers for ligands
stimulating cell-membrane receptors and on controlled release of these
compounds. One can also consider chemical modification of existing bio-
materials to obtain new generation of healing dressings. Such modified bio-
materials can be used not only as the healing dressings but also as scaffolds for
in vitro cell culture or tissue engineering. Tissue growth is strongly stimulated
when a suitable scaffold is present; when the mechanism is known by which the

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cells recognise their solid substrate, one can devise biopolymers (which should
be self-decaying in a few months) which can act as a template for the new tissue
 New biomaterials with properties that were considered „impossible‟ in the
past. Some of the self-assembled bio-materials are of remarkable physical
properties (e.g., spider silk is stronger yet much more flexible than steel). The
understanding of the molecular basis for self-assembly can allow to design and
manufacture materials of unique properties. Another example could be a
combination of antimicrobial activity and selective binding to specific tissue cells
or injectable materials which can be used to repair or strengthen damaged or
weakened tissue, e.g. treatment of stress incontinence and use in
plastic/cosmetic surgery. Natural composite materials with exceptional
toughness, such as nacre ("mother-of-pearl") could also serve as source of
inspiration for the design of novel organic-inorganic nanocomposites. These
materials should be (largely) bio-based or at least bio-inspired. This means that
they are constructed of bio-based building blocks, designed using principles
derived from biopolymers, or made by enzymatic modification of biopolymers.
Bio-based materials
Biopolymers are biocompatible and therefore they have biomedical applications.
biopolymers provide structural support but eventually dissolve away and have been used
in the augmentation and repair of the human body with a high rate of success. They are
used in sutures, staples, and screws. Medical polymers have attracted considerable
commercial interest due to the promises of tissue engineering and the need for
replacement organs.
1.12 Biopolymers in Construction Engineering
Biopolymers clearly dominate the fields of rheology control (dispersing/thinning or
thickening) and water-retention. In the latter application, the market relies almost entirely
on biopolymers.
Biopolymers are used in a great diversity of construction applications.
Biopolymers used in construction applications are: Lignosulfonates, Biopolymers from
Soil, Humic Acid, Lignite, Hydrocarbon-based Biopolymers, Natural Oils Waxes, Bitumen
and Paraffin, Protein-based Biopolymers, Casein, Protein Hydrolysates, Starch and
Cellulose Derivatives, Starch and Derivatives, Cellulose Derivatives, Seed Gums, Guar
Gum, Locust Bean Gum, Exudate Gums and Root Resins, Oil of Turpentine and
Colophonium, Root Resins, Microbial Biopolymers, Xanthan Gum, Scleroglucan, Welan
Gum, Succinoglycan, Curdlan and Rhamsan, Chitosan, Biodegradable Polymers,
Polyaspartic Acid, Polyesters.
Biopolymers with future potential in construction business are: tannins, collagen, gelatin,
carrageenan, tamarind & cassia, Gum Arabic, Gum trigacanth, Gum Karaya, dextran,
pullulan.
Biopolymers for construction
Year of
Introduction
Admixture
chemistry
Function Type of admixture
1920s Lignosulfonate Concrete plasticizer Biopolymer
1940s Lignite Bentonite thinner Biopolymer
1960s Xanthan gum Viscosifier Biopolymer

14
1970s Cellulose ethers Water-retention
agent
Biopolymer
1990s Polyaspartic acid Biodegradable
dispersant, retarder
Biopolymer
Current US Suppliers of Biopolymers
Company Product Application Comments
Zeneca BioProducts BIOPOL resin Films and coatings
Assessing full
production
EcoChem (DuPont)
PLA-PGA
copolymers
Medical and
packaging
100 million lb/year
facility opened in
1995
Cargill, Inc. Polylactide Packaging
10 million lb/year
facility open
Argonne National
Labs
PLA from potato
waste
Packaging Available for license
Warner-Lambert NOVON structural material
100 million lb/year
facility opened in
1992
The Market
For the next 10 years the market for plastics is expected to continue the rapid growth it
experienced in the last half of the last century. World per capita consumption of plastics
is expected to increase from the current level of 24.5 kg to 37 kg by 2010 led by the US,
Western Europe and Japan, but South-east and East Asia and India are expected to
emerge as growth regions to account for 40% of world consumption of plastics by 2010.
World consumption is expected to increase form the current 180 million tonnes to 258
million tonnes in 2010. All plastics resin categories are expected to experience
significant positive growth as further substitution takes place with traditional materials
like steel, wood and glass.
Australian manufacturers (who produce only synthetics), however, are expected to be
seriously challenged in meeting the growth opportunities for resins in both domestic and
export markets. As a result the Australian trade deficit in plastics is expected to grow
significantly to more than $4 billion/year by 2010.
The possible market share for bio-plastics in Australia could range from 10% to 30% of
the polyethylene (PE) resins used in packaging and for making products for agriculture
itself. This would translate to 41,000-123,000 tonnes by 2010. The world market for
biopolymers could be between 4 million and 12.5 million tonnes by 2010, an estimate,
which, it is emphasised, could be well over or well under the actual outcome, depending
very much on the level of R&D applied to developing new bio-plastics resins. This
implies, somewhat conservatively, that bio-plastics could capture between 1.5 and 4.8%
of the total plastics market. To penetrate the plastics market a bio-plastics producer
would need to recognize and deal systematically and comprehensively with several key
issues: a.) economies of scale exist and are important in reducing unit costs; b.) access
to low cost materials of consistent quality; c.) reliable supply and ability to accommodate
market growth; d.) market segmentation for speciality plastics; e.) access to significant
R&D resources to bring about continuous improvements in productivity; f.) supply chain

15
coordination; g.) government regulations; and h.) investor sentiment, which might be
seen as now favouring greater use of renewable resources, providing there is an
improvement in energy efficiency and reduction in greenhouse gas emissions.
Irrespective of environmental benefits of bio-plastics the price of crude oil and naptha
relative to agricultural materials will continue to have a significant influence on the
competitive position of bio-plastics viz. synthetics, though continued improvements in
agricultural material production and processing technologies also have potential to
further narrow the traditional cost advantage of synthetics. Over the past 30 years the
price ratio of agricultural materials:crude oil [$/t:$/barrel] has declined significantly. This
price ratio decline seems likely to continue and narrow the gap between the prices of
synthetic and bio-plastics resins.
Production Possibilities
The production of 41,000-123,000 tonnes of resins for packaging and agricultural inputs
such as films would require an estimated 105,000-316,000 tonnes of, for example,
maize to produce polylactic acid (PLA). An optimal sized PLA plant of 140,000
tonnes/year would require an estimated 350,000 tonnes of maize or equivalent wheat,
sorghum etc.
After examining research and product development of bio-plastics it seems that the main
objective in much of the research has been about the function of biodegradability, with
all other issues including energy efficiency and emission reduction of secondary
concern. Yet for some bio-plastics energy efficiency and emission performance are
among their strongest virtues and biodegradability is not always the most sought
attribute. Also, the essence of the matter of biodegradability is being address, in part at
least, with elaborate recycling of synthetic polymers and even the emergence of
biodegradable synthetics. The real game is about materials performance, sustainability,
use of renewable energy and decreased emissions.
Patel (2) concluded it ‗… is impossible to make a general statement about whether
plastics from biomass are favourable in terms of energy loss and CO2 emissions
compared to petrochemical polymers.‘ Some bio-plastics such as the natural bacterial
based polyesters, polyhydroxyalkanoate (PHA) and its offspring such as PHB, appear to
be relatively less energy inefficient as feedstock (though still quite good compared to
petrochemical polymers) while starch based polymers offer the potential to both save on
energy and reduce CO2 emissions. According to Patel, depending on the share of
petrochemical co-polymers used, starch based plastics offer energy and emission
savings of 12-40 GJ/t plastic and 0.8-3.2 t CO2 plastic in producing PE or an equivalent
biodegradable substitute.
The increased energy consumption and CO2 emissions associated with an increased
share of synthetics in the resin is shown clearly in Table 1. These estimates have been
compiled by Patel from various life-cycle assessments done in Western Europe and
North America. The energy use is non-renewable energy and GHG emissions are
expressed in terms of CO2 equivalents. There is no allowance for the carbon sink effect
of the plants that produced the starch, so the environmental benefits are probably
understated.
Table 1: Emissions and Energy Use: Thermoplastic Starch and Synthetics
Type of Plastics Share of
Petrochemical
Compounds % (wt)
Cradle to
factory gate
energy use 1
Fossil CO2 emissions
throughout life-cycle
(production & waste

16
(Gj/t of
product).
incineration) (kg CO2)/t
product.
TPS 0 25.4 1,140
TPS/polyvinyl
alcohol
15 24.9 1,730
TPS/polycaprolacton 52.5 48.3 3,360
TPS/polycaprolacton 60 52.3 3,600
LDPE 100 80.6 4,840
1
Non-renewable fossil and nuclear energy Source: Patel (2).
The diversity of plant, animal, microbial and marine materials that are used to produce
the above materials is also significant. For this reason, bio-plastics may also be seen as
conducive to biodiversity because the industry has potential to use such a wide range of
genera and species. Also, bio-plastics have potential to use the products of perennial
plants that are being used to solve environmental problems like salinity.
Market penetration by bioplastics, however, may require a fundamental change in
attitude in large parts of the chemicals and plastics industry. Environmental concerns,
along with biodegradable polymers, are seen by many as just another threat to the
traditional industry, rather than a stimulating challenge, to those who practice plant
breeding and the chemistry of plastics in industry, education and research and marketing
of the products. The threat mentality extends up the supply chain to waste management
regimes where biodegradability is seen as an obstacle to existing recycling practices and
down the supply chain to agricultural material production where there is an historical
preoccupation with the food supply chain in plant production and lack of recognition that
industrial product uses for agricultural crops offer benefits in the form of increased
competition at the farm gate and access to growth markets instead of mature markets.
One step in bringing an appropriate level of resources to a new bio-plastics industry
would be to establish a Centre of Excellence in Bio-plastics. The objective of the Centre
would be to develop opportunities for suppliers of agricultural materials as feedstock and
energy for the production of biodegradable and non-degradable plastics. Plant breeders,
chemists and plastics converters would be needed to design and develop a range bio-
plastics resins with high performance in terms of material properties and environmental
attributes.
Algae biopolymer production
United States Patent 4236349
Process and apparatus for the production of algae biopolymer employing a first stage for
the growth of algae and a second stage for biopolymer production is described. In the
first stage, growth of algae biomass in a culture medium is accomplished by operating
the first stage in a continuous mode in which fresh nitrogen-containing nutrient medium
is supplied to the culture. Concomitantly with the supply of fresh nutrient medium to the
culture in the first stage, a portion of the culture medium is transferred from the first
stage to the second stage in which the supply of nitrogen is limited. A nitrogen deficiency
is created in the second stage to shift the culture to a senescent phase to enhance
biopolymer production. The growth phase is carried out in a first stage reaction chamber
which is connected to a plurality of second stage reaction chambers in parallel with one
another. Culture withdrawn from the first stage is transferred sequentially to each of the
second stage reaction chambers such that biopolymer production occurs in several

17
second stage chambers simultaneously with cells produced in the first stage reaction
chamber.
1.13 Problems Associated with Biopolymers
 Environmental Credentials: PLA was first described as biodegradable, but its
manufacturers have since changed the characteristic to ‗compostable‘, meaning
that more heat and moisture is needed to degrade PLA than is found in typical
backyard compost piles. This is a significant change in its marketing and
environmental credentials because the necessary conditions exist in only about
100 US industrial composting sites.
 Additional Sorting: Furthermore, biopolymers (except for future PE/PP made
from sugar cane) are a problem for commercial recycling centers because they
require additional sorting to avoid contaminating other material streams, and,
although segregated collection helps, it is complex and increases costs. The
most interesting solution to this problem is chemical recycling, which breaks
down all types of scrap polymers into feedstocks. This is perhaps the most
promising recycling solution for all polymers which is not subsidized.
 More Total Energy: So far, biopolymer producers have had problems
demonstrating that their materials have smaller carbon footprints than fossil fuel-
derived polymers. The energy inefficiencies of planting, growing, and transporting
biological feedstocks mean more total energy is likely consumed to produce a
unit of biopolymer than to make a unit of an oil or gas-based polymer.
 CO2 Emissions: NatureWorks, the largest producer of PLA, claims on its
website that its PLA has a low carbon footprint, and says it uses ISO 14040 to
calculate the carbon footprint but provides no data. In addition, the NatureWorks
website states that it buys wind energy certificates to offset its manufacturing
carbon footprint, but this is hardly specific to this company, and any firm can do
this for any product and claim it to be carbon neutral. In any case, carbon
footprints may be an irrelevant measurement. It has been established that plants
grow more quickly and are more drought and heat resistant in a CO2 enriched
atmosphere. Many studies have shown that worldwide food production has risen,
possibly by as much as 40%, due to the increase in atmospheric CO2 levels.
Therefore, it is a great irony and a significant potential problem for biopolymer
production if the increased CO2 emissions from human activity were rolled back
because this would cause worldwide plant growth to decline, greatly increasing
competition for biological sources of food and fuel with biopolymers coming in
last place.
 Confusing Environmental Terminologies: The contradictory or confusing use
of environmental terminology can turn the public against green initiatives.
Sustainability has as many meanings as the people and groups using the word,
but few are based on consistent, realistic principles and facts. The careless,
confusing, or deliberate misuse of the term green hurts all efforts to be
environmentally responsible and has thus become tagged ‗greenwashing.‘
 Competing for source materials: Government involvement in environmental
initiatives, such as producing ethanol from corn for motor fuel use, has brought
political baggage that confuses and distorts the original purposes and its ultimate
usefulness. Since government programs are seldom revisited, they can often
result in stifling future innovation and responsible policy changes. Biopolymers
have had an important place in the plastics industry for centuries and will
continue to do so, but are unlikely to be across-the-board replacements for
conventional polymers because their primary value proposition is realized as

18
specialty materials. Biopolymers will be competing for source materials with
government mandates that strongly favor producers of alternative fuels.
 Seasonal Variations: Finally, it is important to remember that weather is always
the key factor in the supply of cultivated crops, and since it cannot be controlled,
the result is the unpredictable seasonal variations in prices which will affect
supply and demand.
Some biopolymers are biodegradable: they are broken down into CO2 and water by
microorganisms. In addition, some of these biodegradable biopolymers are
compostable: they can be put into an industrial composting process and will break down
by 90% within 6 months. Biopolymers that do this can be marked with a 'compostable'
symbol, under European Standard EN 13432 (2000). Packaging marked with this
symbol can be put into industrial composting processes and will break down within 6
months (or less). An example of a compostable polymer is PLA film under 20μm thick:
films which are thicker than that do not qualify as compostable, even though they are
biodegradable. A home composting logo may soon be established: this will enable
consumers to dispose of packaging directly onto their own compost heap. The standards
for such a home composting logo have not yet been developed.
1.14 Additives for Biopolymers
Several performance enhancing additives have been developed in recent years for
biopolymers. Additives for biopolymers are being investigated on three levels.
First involves traditional additives that have no adverse effect on health or the
environment and do not compromise resins‘ compliance with compostability standards.
Second are renewable additives derived from natural sources, but not necessarily
biodegradable, for use in durable products.
Third are additives that are both renewable and biodegradable, which are a good fit for
single-use or short lived products.
When additives are added to biopolymers and other plastics intended for composting,
they must meet standards for compostable plastics such as ASTM D6400 and its
European Union counterpart, EN 13432. However, a shift of interest has been seen from
compostability to renewability in USA. This is partially because of lack of composting
infrastructure in USA as compared with Europe, Japan and even China. However,
compostable biopolymers are existent in USA on a small scale.
Processors require to incorporate additives in those biopolymer that are offered
uncompounded, while other producers offer fully compounded products that may only
need addition of colorant. A few companies have developed conventional and biobased
additives to enhance processing of biopolymers such as PLA, PLA blends, PHA,
Ecoflex, and starch resins.
Key issues for improved physical properties of biopolymers include (i) impact
modification, (ii) heat resistance, (iii) barrier performance, (iv) UV resistant property, (v)
antioxidant property, and (vi) anti fog properties.
Melt strength, which can hinder extrusion, blow molding, foaming, and deep-draw
thermoforming, is a common limitation of PLA and other biopolymers. Recognizing this
need, Arkema introduced Biostrength 700 acrylic-copolymer processing aids, which can
double the melt strength and extensibility of PLA at a 4% loading while maintaining
transparency. Melt strength is essential to good cell structure in foams, which are an
area of keen interest for biopolymers like PLA. There have been challenges in foaming
PLA as well as other biopolymers, as most are crystalline, and the foaming agents
release water. Water tends to degrade biopolymers in the melt phase and cause further

19
loss of melt strength and physical properties. Reedy has just introduced two new
foaming agents designed for PLA and PET. They are combination endothermic foaming
agents and melt-strength. PLA is very sensitive to acid, hence requires a moisture and
acid scavenger that is both reactive and absorbent.
One way to enhance melt strength for foams and other uses is with Clariant‘s CESA-
extend chain extender, an epoxy-functional styrene/acrylic oligomer provided as a
masterbatch in a variety of carrier resins. Originally developed to restore the molecular
weight or I.V. of recycled PET and nylon, CESA-extend can re-link polymer chains that
have broken due to thermal, oxidative, and hydrolytic degradation. Recently it has shown
great promise in PLA, and similar results are expected for PHA. When 2% of CESA-
extend was added to NatureWorks‘ PLA 4042D, the average molecular weight was
raised by 49%, indicating branching extension of the polymer chains and higher
molecular weights. After modification, PLA‘s elastic modulus decreased by about 20%
while its elongation was raised by 50%. These effects make it possible to use direct gas
injection to produce a nucleated foam structure with small cells, smooth surface, and up
to 15% weight reduction. CESA-extend appears to cause a change in PLA‘s rheology
from its typical Newtonian behavior to some degree of shear-thinning, non-Newtonian
behavior after chain extension. This effect and higher melt strength assist in blown film
extrusion. CESA-extend permits running less noisy film at higher speeds, permits
doubling the bubble size, and maintain better bubble-size uniformity.
Ampacet has developed slip and antiblock concentrates for PLA and PHA. It is working
with chain extenders and chain-entanglement agents to develop melt-strength
enhancers for PLA.
Elvaloy copolymers of DuPont work well as processing aids to help various types of
biopolymers feed better during injection molding. In addition, it‘s Biomax Strong 100 and
120 ethylene copolymers, developed to toughen PLA, also act as processing aids that
significantly reduce screw torque and improve melt stability.
PolyOne has a range of impact-modifier masterbatches, including those in its bio line for
opaque and transparent biopolymer systems. DuPont‘s Biomax 100 and 120 improve
toughness and reduce brittleness in PLA rigid molded and thermoformed parts. At 1-3%
loadings, they outperform competitive tougheners with little effect on transparency.
Paraloid PMA 500 acrylic impact modifier from Rohm & Haas is used to boost impact in
PLA and is likely to work well in other biopolymers.
Arkema offers new Biostrength 130 acrylic modifier, which retains adequate
transparency for translucent PLA applications, and Biostrength 150 MBS-type modifier
for greater toughening in opaque applications.
Ciba has added natural antioxidants like vitamin E to the line, as well as aroma
masterbatches based on natural oils for biopolymers.
PolyOne continues to explore technologies to enhance the heat resistance of biobased
resins, particularly PLA and starch blends. PolyOne offers additive masterbatches that
control moisture fogging of the interior surfaces of transparent biobased packaging.
For UV resistance, both Clariant and PolyOne have developed biobased UV-stabilizer
masterbatches that protect the contents of transparent biopolymer packaging.
DuPont plans to introduce soon Biomax Thermal 120, a proprietary heat-distortion
modifier that will allow PLA thermoformed parts to withstand hot transport and storage.
In addition to traditional pigments that can be used in biopolymers, bio-derived colorants
are now available from at least four companies. Clariant‘s Renol-natur color
concentrates are derived mainly from plants and include red, orange, yellow, and green,
with blue in the final stages of development. These colors are very earthy and organic
looking, and some have excellent clarity, though their light fastness is not as high as

20
traditional colorants. Various biopolymers can serve as carriers for these masterbatches.
PolyOne‘s bio color concentrates and liquid colorants are based in part on sustainable
raw materials. The concentrates use biopolymer carriers such as PLA, PHA, modified
starch compounds, and biodegradable polyesters. Opaque colors are available for all
these biopolymers, but transparent colors are also available for PLA.
Teknor Apex recently launched color concentrates for PLA resins and blends aimed at
packaging, bags, liners, and other extruded or molded products. Three series of
colorants are offered for clear or opaque bottles, film, sheet, profiles, and injection
molded items. The carrier resins are either PLA or compatible polyesters (including
PET). Organic and inorganic pigments are used, depending on the end-use
requirements. The pigments produced from plants are more expensive and may be less
consistent. Also, the colors are not as vibrant, leading to fewer color options.
References:
Sustainable Materials http://altprofits.com

21
CHAPTER 2
BIOGUMS (BIOPOLYSACCHARIDES)
2.1 Introduction
2.2 Sources of Polysaccharides
2.3 Microbial Polysaccharides
2.4 Probable Role of Extracellular Polysaccharides
2.5 Market for Microbial Polysaccharides
2.6 Biopolysaccharides from other Sources
2.6.1 Starch
2.6.2 Carrageenan from Seaweeds
2.6.3 Alginate from Seaweeds
2.6.4. Guar Gum
2.6.5 Chitin & Chitosan
2.7 Advantages of microbial gums
2.8 Important Microbial gums
2.8.1 Xanthan
2.8.2 Pullulan
2.8.3 Curdlan
2.8.4 Scleroglucan
2.8.5 Dextran
2.8.6 Alginate
2.8.7 Gellan
2.8.8 Levan
2.8.9 Hyaluronic Acid
2.8.10 Welan
2.8.11 Zooglan
2.8.12 Succinoglycan
2.8.13 Emulsan
2.8.14 Biodispersan
2.8.15 Zanflow
2.8.16 Polymer S-130, S-194 and S-198
2.8.17 Xylinan (Acetan)
2.9 Companies Producing Biogums
2.10 Commercial Production of Microbial Gums
2.11 Exopolysaccharides from Mushroom
2.12 Exopolysacchardies from Archaea
2.1 Introduction -
Microbial polysaccharides came into use in 1940 with discovery of ‗Dextran‘ which found
use as blood plasma extender. Then in 1960, ‗Xanthan‘ gum was developed by a group
of scientists in Kelco Company in USA. Although biogums are not much known in India,
it is a big business in the US and Europe. Biogums are used as suspending, thickening
and gelling agents mainly in foods and pharmaceuticals. World-wide sales of microbial
polysaccharides were US$ 300 million as per 1992 reports. The food industry worldwide
uses 70 000 tonnes of polysaccharides per year as thickening agents, stabilizers and
texturizers.
These biopolymers are valued primarily for their ability to act as thickeners, and
as hydrophilic colloids to emulsify, suspend, and stabilise mixtures in water-based

22
systems. They often exhibit compatibility and synergy with one another, under wide
variety of pH, temperature and salt conditions. The Kelco Division of Merck & Co. is the
world‘s largest leading manufacturer of biogums. The company has recently announced
plans to undertake $29 million expansion of its biogum production at San Diego and at
Okumulgas (Oklahoma). Biogums are produced by fermentation at both the plants.
Many microbial exopolysaccharides (EPS) have been described in some
structural detail and might have ‗useful industrial properties‘, but polymers from
pathogenic microbial species are unlikely to be acceptable. Only those microbial
polysaccharides which show good yield and have properties superior to xanthan,
curdlan, or gellan or traditional plant and algal gums are likely to develop. Several
microbial polysaccharides are now widely accepted commercial products. Major
technological development is required in the recovery of microbial gums from
fermentation broth and its drying. Effective use of ligno-cellulosic wastes or whey as
carbon source for producing microbial gums would be advantageous.
2.2 Sources of Polysaccharides
Plants, Algae, microorganisms are the sources of polysaccharides. Although
plants produce a wide range of polysaccharides, their diversity is considerably less than
those produced by micro-organisms. This more diversity in microbial polysaccharides is
due to some 200 different sugars found in them compared to only about 25 sugars
associated with polysaccharides of plant origin. Geographical and climatic constraints
have limited production of plant and seaweed polysaccharides to certain part of the
world only.
Although many microbial polysaccharide structures have now been elucidated,
industrial usage of polysaccharides (gums) still relies extensively on material obtained
from plants or marine algae. Such traditional commercial polysaccharides include starch,
dextran, alginate, gelatin, carrageenan, gum Arabic, gum tragacanth (used in
toothpaste), china grass (used in jams and jellies) and the plant glycomannans - locust
bean gum, gum guar and konjac mannan which are widely employed in the food and
pharmaceutical industries. All the gums from plant or algal sources do not have desired
rheological properties. Microbial polysaccharides provide replacements for gums in
current use, or novel materials with unique or improved rheological characteristics which
may find new applications.
Microbial polysaccharides are widely used in food industry as functional
ingredients. Their main application is in the rheological control of the aqueous phase.
Many polysaccharides perform as simple thickeners. Polysaccharides which are used as
simple thickeners in the food industry include sodium alginate, carboxymethyl-cellulose,
the plant seed galactomannans, and A-carrageenan.
They differ from each other quantitatively rather than qualitatively, and in general
the cheapest find greatest application.
Here the polysaccharide molecules exist as fluctuating disordered chains
(random coil). Their viscosity behaviour is non-specific, in that when molecular weight is
normalized for, a general pattern describing the shear dependence and the
concentration dependence for all polysaccharides of this type can be seen.
The polysaccharides are classified according to their uses (i) as viscosity-
increasing agents (ii) as gelling agents (iii) polysaccharides with specific applications
such as tailor-made dextran and pullulan and (iv) polysaccharides used as substrates for
the preparation of rare sugars.
Factors limiting the commercial potential of certain microbial polysaccharides are
availability, rheological properties, and polyvalency.

23
Current interest in glycobiology and the application of new analytical methods
has also stimulated academic research on microbial polysaccharides. However, there is
a gap between our knowledge of the structure of polysaccharides and the ability to
predict their physical properties, and thus their potential applications.
Although many researchers have found polysaccharides ‗of superior viscosity to
xanthan‘, in reality few match the robustness of the Xanthomonas polysaccharide and
few can maintain their physical properties in the presence of salts, at higher
temperatures or extremes of pH. Most are unlikely ever to find a niche in the
polysaccharide market place.
2.3 Microbial Polysaccharides
Microbial Polysaccharides may be (1) exocellular polysaccharides (2) structural
polysaccharides (3) intracellular polysaccharides.
Microbial Polysaccharides can be produced in one of the two forms:
(i) Capsular Polysaccharides (C.P.S.) (ii) Exo-polysaccharides (E.P.S.)
Many bacteria, yeasts and fungi produce them.
Cellwall polysaccharides and intercellular polysaccharides (microcapsule) belong
to first category i.e. capsular polysaccharides and are difficult to separate from cell
biomass and are not important commercially. Yeast glucan starch, fungal chitin are the
examples of first category. Structural polysaccharides present in cellwall or as
microcapsules or one which are intracellular are difficult to separate from cellmass and
hence have less commercial importance.
Capsular polysaccharides (C.P.S) protect pathogenic micro-organisms from
immune system defenses and infection by bacteriophage by providing a physical barrier.
The exocellular polysaccharides, which constantly diffuse into the cell culture
medium making it slimy and viscous, are easy to isolate from the culture media, free
from protein and cell debris. Xanthan, Dextran, Gellan, Wellan, Curdlan are the
examples of second category.
For the production of microbial polysaccharides the main interest is in that of
EPS. EPSs of microbial origin have unique properties in their capability of forming very
viscous solutions at low concentrations and their pseudoplastic nature. Those produced
by lactic acid bacteria have been considered very important in use for food emulsifiers
and thickeners throughout the years.
Microbial EPSs can be divided into homopolysaccharides and
heteropolysaccharides. Most homopolysaccharides are neutral glucans, while the
majority of the heteropolysaccharides are polyanionic due to the presence of uronic
acids. Further contributions to charge come from pyruvate ketals or succinyl half-esters.
At present, very few EPSs are available commercially, but the number and their
applications are gradually increasing. Some of the microbial polysaccharides such as
xanthan (the EPS from Xanthomonas campestis pv. campestris) are already well
established by modern biotechnology and have a sizable market. Others such as
pullulan possess potentially useful chemical and physical properties.
Yeast glucan, which is somewhat similar to starch and fungal chitin are typical
examples of capsular polysaccharides, while xanthan, dextran, curdlan, welan and
gellan are typical exocellular polysaccharides. Microbial polysaccharides can be either
homo or hetropolysaccharides.
2.4 Probable Role of Extracellular Polysaccharides (E.P.S.) in Nature
The production of extracellular polysaccharide represents a significant expenditure of
energy, so it must serve some purpose.
(i) One of its roles could be to ensure a moist environment around the cells,

24
where nutrients can diffuse through the slime.
(ii) Another role could be to avoid recognition of a pathogenic bacterium by the
host, because extracellular slimes do not usually have antigenic properties.
(iii) Yet another role could be to restrict oxygen diffusion towards the cells - a
particularly important feature for nitrogen-fixing bacteria such as Rhizobium
and Azotobacter species, because the nitrogenase enzyme responsible for
nitrogen fixation is extremely oxygen-sensitive. At 20o
C, oxygen diffuses
almost exactly 10,000 times more slowly through water than through air, so
even a thin covering of hydrated slime could help to regulate the exposure of
cells to oxygen.
(iv) One more role of slime has been demonstrated for the important plant
pathogen Pseudomonas solanacearum. This bacterium causes vascular wilt
diseases of a range of crops, by gaining entry to the water-conducting
(xylem) vessels. It then produces extracellular slime which blocks the vessels
and leads rapidly to plant death
2.5 Market for Microbial Polysaccharides
Market for some food gums are –
No. Gum Amount (Lbs x 106
) Price $ / Lb
1 Guar 12 0.5
2 CMC 12 1.5
3 Arabic 12 2.0
4 Xanthan 1.9 6.1
5 Carrageenan 6.0 3.0
In price per unit weight, CMC is three times, gum arabic four times and xanthan gum
about twelve times that of guar gum
Demand for Microbial Polysaccharides
No. Microbial
Polysaccharides
Demand in USA
(lbs. × 106
)
Price in USA
($ per lb)
Demand in India
1 Xanthan 6.9 6.1
2 Carragenan 6.0 3.0
3
2.6 Biopolysaccharides from other Sources
2.6.1 Starch
Starch is unique among carbohydrates because it occurs naturally as discrete
particles, called granules. The granules are the primary means of energy storage in
green plants over long periods of time, and the shape and size of the granules depend
on their origin. Starch granules from canna and white potato are among the largest;
those from rice and buckwheat are among the smallest. While it has long been known
that the larger granules of any particular type of starch, such as corn, gelatinize more
easily than the smaller granules, it would now appear that there may be some correlation
between the dispensability of a type of starch and its average granule size6. Starch

25
granules vary in size from about 2 mm to 150 mm. Pure starch, as distinct from
commercial starch, is a white, odourless, tasteless, neutral powder, insoluble in cold
water or organic solvents8. Most starch granules are composed of a mixture of two
polymers9, namely amylose and amylopectin. The amylose content can vary over a
broad range, from 0 to about 75%, but typically is 20–25% (w/w). The ratio affects the
physical and chemical properties of a particular starch, as well as subsequent
mechanical processing. Dry starch is not thermoplastic. However, processing by: (1)
extrusion and incorporation of plasticisers, (2) graft copolymerisation, (3) preparation of
blends with thermoplastic polymers and chemical modification, have all been studied as,
means to prepare packaging materials.
Starches from different sources vary, particularly in their qualitative and
quantitative make up, as well as in some of their physiochemical functional properties.
Starch is a natural polymer. Starch can be processed directly into a bioplastic,
but because it is soluble in water, articles made from starch will swell and deform when
exposed to moisture, limiting its use. This problem can be overcome by modifying the
starch into a different polymer.
Thermoplastic Starch
The addition of a plasticiser such as water to starch renders it thermally
processable. When gelatinisation takes place in abundant water at temperatures below
100°C, no depolymerisation of starch occurs. Films have been prepared by the casting
and drying of dispersions of gelatinised starch in water-glycerol mixtures. But, the
hydrophilic nature of starch is a major constraint that seriously limits the development of
solely starch-containing materials, and starch gelatinisation itself is not enough to
prepare a viable, thermoplastic material.
When starch is converted to produce thermoplastic material in an extruder, it is
termed destructurised or thermoplastic starch. In extrusion, starch is converted by
application of both thermal and mechanical energy, and basically three phenomena
occur at different structural levels: fragmentation of starch granules; hydrogen bond
cleavage between starch molecules, leading to loss of crystallinity; and partial
depolymerisation of the starch polymers. Furthermore, the extrusion process ensures
the very intimate mixing of the polymers and any additives.
Molecules such as polyglycols, amides and amines serve as non-volatile
plasticisers for starch. Water, by contrast, will evaporate from starch films leading to
embrittlement. Because of the inherent hydrophilicity of starch, the performance of
extruded starch/ plasticiser mixtures may change with time as any water content
changes. In the cases where non volatile plasticisers are employed and under certain
conditions of temperature, pressure, shear, limited water and sufficient time, starch may
be successfully extruded or injection moulded to produce a viable and commercial
thermoplastic material.
Depending on the starch source and processing conditions, a thermoplastic
material may be obtained with mechanical properties suitable for structural applications.
The main use of destructurised starch alone is in soluble compostable foams such as
loose fills, expanded trays, shape-moulded parts, expanded sheets and as a
replacement for expanded polystyrene.
Thermoplastic material enhanced by the presence of plant fibres, food additives,
and water that is coextruded and injected into moulds have been reported. After
demoulding and humidity equilibration, a stable and flexible material was obtained. This
biocomposite could only be used for the production of tray-like forms, in which good
mechanical properties were not required. It has been observed that of the low oxygen
permeability of coatings and films prepared from amylose and amylomaize starch at 5 to
25°C and at relative humidities up to 100%. This work highlighted the potential value of

26
such processed starches as components of multilayer films. Such gas barrier
characteristics may permit the modified atmosphere packaging of, for example, raw
meat or fresh fruit and vegetables and thus extend the shelf life of the packaged goods.
Graft Copolymerisation
Graft copolymerisation of thermoplastic polymers onto starch provides another
method for preparing starch-polymer composites. An important advantage of graft
copolymerisation is that starch and the other polymer are bound covalently rather than
by looser, non-covalent interactions as an associated mixture. In the case of graft
copolymerisation, the two dissimilar polymers are more intimately associated, and the
separation of two distinct polymer phases is unlikely to occur. Polymethylacrylate is often
the copolymer of choice but polymethylacrylate is not biodegradable. Biodegradation has
therefore been enhanced by copolymerizing vinyl acetate with methyl acrylate during the
grafting reaction. The so-formed polyvinyl acetate is de-esterified by esterase enzymes
and the resulting polyvinyl alcohol can then undergo further microbial attack.
Preparation of Blends
In order to overcome the inherent hydrophilicity of starch, blends with
conventional hydrophobic synthetic polymers (e.g. polyethylene or polypropylene) have
been considered for the production of plastic bag and commodity products. However, the
physical mixing of non-biodegradable polymers with 6-20% of starch affords materials in
which only the starch portion is biodegradable, leaving the porous and hardly
biodegradable synthetic polymer behind. This approach, therefore, cannot be
recommended. Blending with more hydrophobic and biodegradable polymers
(polyesters) produces formulations that are suitable for injection moulding and blown
films. Starch can be destructurised and compatibilised with different synthetic
polyestersto satisfy a broad spectrum of market needs. To reduce the sensitivity of
starch to water it is blended with more hydrophobic, thermoplastic materials such as
polycaprolactone, polyhydroxybutyrate/valerate and cellulose acetate. Such blends are
completely biodegradable under composting and other biologically active environments.
A biodegradable starchpolycaprolactone blend has been reported by Novamont (Italy)
and commercialised under the trade name Mater-Bi Z-class. Narayan (USA) has
developed a process technology involving reactive processing of plasticised starch with
modified polycaprolactone in a twin-screw extruder. A number of smaller manufacturers
supply their own variations of starch/biodegradable polyester blends. These companies
include Biotec, Earthshell and Biop. Commercially available products based on starch
blends include agricultural mulch film, twines, ropes, pots, foams for packaging, soluble
loose fill and shape-moulded parts.
Chemically Modified Starch
Industry already produces chemically modified starches for a number of end
uses, but such derivatives are targeted at the surface modification of intact granules.
However, a fully satisfying solution to the design of high performance materials from
starches remains elusive. Specifically designed starch materials that can be easily
prepared will be of great importance for future application of starches in thermoplastic
applications. The modification route is likely to be costly, although starch is less
crystalline and more chemically accessible than cellulose. Thus, chemical derivatisation
has been studied as a way to improve thermoplasticity and to produce water-resistant
materials. Depending on the nature of the substituents and on the degree of substitution
(DS), the properties of the modified starch can be varied extensively. Esterification with
organic acids is known to result in thermoplastic and hydrophobic materials when the DS
is high enough.
BioComposites Centre (UK) has developed a route to chemically modified,
hydrophobic starches. A range of variously substituted (DS 0.5–3.0) maize, potato and

27
wheat starches has been prepared and films cast from solvent. Films are water resistant
and flexible. Flexibility can be enhanced by application of naturally occurring, food grade
plasticisers. Additionally, for hydrophobic thermoplastic starches in which the chemical
modification technology is tightly controlled, one can tailor, for example, the barrier
properties (e.g. gas barrier and moisture vapour transmission rate) to achieve specific
functionality. A project is focused on the use of modified starch film as a laminate
component in combination with other polymers, such as low density polyethylene and
polystyrene.
2.6.2 Carrageenan from Seaweeds
Carrageenan is extracted from various species of red algae including Chondrus
crispus and Mastocarpus stellatus both of which are found in the Western Isles although
only small quantities are present. Carrageenan is used to gel, thicken or suspend, most
frequently in food production, especially dairy products. The principal suppliers of
seaweed for carrageenan extraction are the Philippines, Canada, Chile and Europe.
While production from other countries has been fairly static in the last 20 years,
seaweed farming in the Philippines has grown steadily during this period, and this
country is now the source of over half the world's supply of seaweed used in
carrageenan production.
FMC Biopolymer, Philadelphia, PA 19103, USA is a producer of carrageenan.
The development of seaweed culture in the Philippines has helped to stabilize
supplies and prices in this sector, and throughout the 1980s production capacity
moderately exceeded demand. With regard to carrageenan itself, around 90% of the
world's supply comes from five processors in Denmark, France and USA.
Carragenan is sold as mixture of three main forms – Kappa, Lambda and Iota.
There is a Galactose backbone. Ester sulfate gives negative charge Gels with potassium
(Kappa), Gels with calcium (Iota) and Non-gelling (Lambda). It is good stabilizer for milk
proteins Suspender for chocolate in milk, gels with TSPP Part of ice cream stabilizer,
mix Water gels.
Carrageenan (Kappa Form) Carrageenan (Lambda Form) Carrageenan
(Iota Form)
2.6.3 Alginate from Seaweeds
Alginate is extracted from large brown seaweeds from regions with water
temperatures of ca 200
C or less. Lower viscosity alginate is also produced from warm
water species. In terms of volume of supply Macrocystis, Laminaria and Ascophyllum
are the most significant algae (all cold water species). Today Kelco are the largest
producer of alginate, with the major competitors located in Norway, France, Japan and
China .
Many countries supply seaweed as a raw material to the alginate industry. These
include USA, Mexico, Chile, Scotland, Ireland, France, Norway, Iceland, Canada, China,
Japan, Korea, Australia and South Africa
In China and Japan Laminaria is cultivated intensively. The bulk of production is
distributed to the higher value food sector in the Orient. In Europe however the bulk of

28
brown seaweeds harvested are sold to the alginate industry with relatively minor
amounts used as raw materials in other sectors such as fertilisers, food,
pharmaceuticals, etc.
There are several hundred applications for alginate in a variety of industries. Its
main uses are as a thickening or suspension agent, gel and film formation, stabiliser,
binding agent and for water retention
Alginate is used in textile industry (50%), food industry (30%) and remaining
share is of pharmaceuticals, paper industry and others.
2.6.4 Guar Gum
Guar gum is obtained from the seed of the legume Cyamopsis tetragonolobus,
an annual plant that grows mainly in semi-arid regions of India. The structure of the
polysaccharide consists of a main chain of (1-4)-linked β-D-mannopyranosyl units with
single α-D-galactopyranosyl units linked (1-6) on average to every second main chain
unit. Guar has a high viscosity in aqueous solution, shows marked pseudoplastic
behaviour and forms synergistic gels in the presence of other gums such as
carrageenan and xanthan gum.
2.6.5 Chitin & Chitosan
Chitin is a polysaccharide which is found widely in nature where it functions in a
manner similar to collagen in chordates. It forms the tough fibrous exoskeletons of
insects, crustacians and other athropods, and, in addition to its presence in some fungi it
occurs in at least one alga. The structure of chitin is similar to that of cellulose but with
glucose replaced with Nacetyl-D-glucosaminyl units linked β-D-(1-4) in a linear chain. It
is normally produced from the shells of lobster, crab or shrimp.
Chitosan is the deacetylated form of Chitin. The polysaccharide is deacetylated
in order to render it soluble which is then possible at pH values of less than 7 normally in
dilute acid. This then allows the material to be used in a number of industrial applications
as a binder and film former.
2.7 Advantages of Microbial Polysaccharides (Microbial Gums) –
Microbial gums can have certain advantages and newer applications than
traditional plant and algal gums.
1. The collection of gums from plants is laborious process and requires skilled
labour.
2. Seasonal variations affect both quality and quantity of gums that can be obtained
from plants which is not a problem with microbial gums.
3. With traditional supplies of gums from plant or marine algae sources problems
can arise due to crop failure, drought, war, climatic conditions or to marine
pollution, famine and disease which is not the case with industrial production of
microbial gums. High technology equipment, well-trained staff and adequate
power and water supplies, however is required for production of microbial gums.
4. Microbial gums have unique rheological and phsico-chemical properties. The
rising commercial importance of microbial gums is due to their ability to alter the
flow properties or rheological characteristics of aqueous solutions.
5. The viscosity of microbial gums is not significantly affected by acids, alkalies,
salts, surfactants (soaps and detergent chemicals) and organic solvents even
after a prolonged contact of 3 months. Better resistance of solutions of microbial
polysaccharides to degradation by acids, alkali, free radicals, hydrolytic enzymes,
shear forces is due to their ordered conformation (single/double/triple helix
structure of regular repeating units of monosaccharides).

29
6. They often exhibit compatibility and even synergy with one another and under
wide variety of temperature, pH and salt conditions.
7. Microbial polysaccharides show strong pseudoplastic behaviour (reduction of
viscosity with shear and recovery of viscosity when shear rate is decreased)
which distinguishes solutions of microbial polysaccharides from other thickeners.
2.8 Important Microbial gums
2.8.1 Xanthan
It was discovered by an extensive research effort by Allene Rosalind Jeanes and
her research team at the United States Department of Agriculture, which involved the
screening of a large number of biopolymers for their potential uses. Xanthan Gum was
discovered in the 1950s at the Northern Regional Research Center (NRRC), Peoria,
Illinois. Xanthan has been commercially produced in USA since 1961 and was approved
for addition in food since 1969. It was approved in Europe for food use in 1982. More
than 20,000 tonnes of xanthan is produced world-wide per annum. It was brought into
commercial production by the Kelco Company under the trade name Kelzan in the early
1960s. Cost of Xanthan used mainly in food applications was US$14 per kg in 2009.
Chemical structure
Xanthan is made up of beta-D-glucose units which are linked in a way identical to
the linkages between the glucose units of cellulose. Each alternate glucose in the chain
is attached with a trisaccharide side chain consisting of two mannose sugar molecules
and a glucuronic acid molecule. [Structure – Xanthan gum is polyelectrolyte with a β-(1-
4)-D-glucopyranose glucan (like that in cellulose) backbone with side chains of –(3-1)-α-
linked D-mannopyranose-(2-1)- β-D-glucuronic acid-(4-1)-β-D-mannopyranose on
alternating residues. Around 40% of the terminal mannose residues are 4,6-pyruvated
and the inner mannose is mostly 6-acetylated (that is, the side chains are mainly β-D-
mannopyranosyl-(1-4)-(α-D-glucopyranosyl)-(1-2)-β-D mannnopyranoside-6-acetate-(1-
3)-. Some side chains may be missing. ]
Xanthan has a cellulosic backbone on every second glucose residue of which a
trisaccharide side chain is attached. This unusual structure confers physical properties to
the polymer which are utilized in food and other industries.
Molecular weight of Xanthan varies from 2 X106
to 20 X106
Da
Fig. 2. Structure of Xanthan
Properties
(1) Xanthan is stable at both acid and alkaline pH and forms pseudoplastic
dispersion in water.

30
(2) Relatively low polysaccharide concentrations produce highly viscous
solutions and the viscosity does not change greatly on raising the
temperature.
(3) The solutions are compatible with many other ingredients in food and give
good flavour release.
(4) Xanthan is also a good suspending and stabilizing agent for oil/water
emulsions such as salad dressings. Because of all these features and its
inherent safety, xanthan received GRAS listing (Generally Regarded As Safe)
for food use in the US after its initial discovery in the USDA laboratories in
Peoria and its development by KELCO. Subsequently, the polysaccharide
received approval in the EU.
(5) The gum itself is colourless. The bacteria have a yellow pigment in the wall,
but it is extractable only with organic solvents so it does not interfere with the
commercial processing of Xanthan.
(6) Xanthan Gum is yellowish powder.
(7) Xanthan has a little bad smell.
(8) It is dissolved in water.
(9) It is acid-proof and can resist alkali and heat.
(10) Xanthan Gum has good increasing stickiness, false plasticity, particle
stability, and emulsification.
(11) It is nonpoisonous for people and animal. It is esculent. Meanwhile, it can
be used extensively in such fields as food, oil extraction, papermaking, water
treatment, ore dressing, medicine, etc.
(12) Xanthan gum is tasteless and does not affect the taste of other food
ingredients. The caloric value of Xanthan gum is very low (0.6 kcal/g).
(13) Xanthan has practically all the functional properties, required of a
hydrocolloid for different applications. Thus it has thickening, suspending,
suspension and emulsion stabilizing and gelling properties.
(14) It has high shear thinning rheology, with a high yield value and can have
thixotropic or gelling behaviour, depending upon conditions.
(15) Additionally it has good shear, thermal and pH stability. All these
properties make it an excellent food hydrocolloid.
(16) Xanthan has extraordinary chemical stability. In strong acid or base
conditions its aqueous solutions are stable for several months at room
temperature.
(17) The high viscosity of dilute xanthan solutions stays uniform over a
temperature range of 0-100o
C.
(18) Xanthan displays unusual flow behavior. In the absence of shear stress, a
xanthan solution is viscous, but when a shear stress is applied beyond a
certain low minimal value, the viscosity decreases sharply with shear rate.
Industrially used Xanthan comprises of 37% glucose, 43.4% mannose, 19.5%
glucuronic acid, 4.5% acetate and 4.4% pyruvate. The viscosity of the Xanthan gum
depends on the terminal pyruvate number and molecular mass.
Uses
Xanthan gum is mainly considered to be non-gelling and is used for the control of
viscosity due to tenuous associations endowing it with weak-gel shear-thinning
properties.
It hydrates rapidly in cold water without lumping to give a reliable viscosity so that
it can be used as thickener, stabilizer, emulsifier and foaming agent. One of the most

31
remarkable properties of Xanthan gum is its capability of producing a large increase in
the viscosity of a liquid by adding a very small quantity of gum, on the order of one
percent. In most foods, it is used at 0.5% and can be used in lower concentrations. The
viscosity or thickness of Xanthan solution decreases when it is subjected to shear
pressure.
As soon as the pressure is released the gum returns to its original viscosity. This
property of instantaneous viscosity reversal is known as non-Newtonian behaviour. In
other words, xanthan gum shows pseudoplasticity.
Xanthan gum is best suited for enhanced oil recovery operations due to its
special rheological properties. Xanthan gum is stable under wide range of pH and
temperature. The commercial production requires a very high level of engineering and
technical expertise as well as marketing skills.
Physical properties of Xanthan make it useful as a stabilizing, emulsifying,
thickening and suspending agent.
In non-food applications, particularly in oil-field applications it surpasses its
nearest rival, guar gum in being more thermostable, and stable to acids and most of the
enzymes. In oil drilling and enhanced oil or gas recovery it has an edge over guar gum in
being shear stable, having high viscosity at low concentration, low residue after break,
conditional gelling, compatibility to common additives, and in being useful in hot and
deep wells.
Xanthan has been placed under Generally Regarded as Safe (GRAS) category
for use in food or pharmaceutical formulations in USA, EU and in a number of other
countries.
Preparation
Xanthomonas campestris produces ‗Xanthan‘ biopolysaccharide as a by-product
of its metabolism. Xanthan is naturally produced to stick the bacteria to the leaves of
cabbage-like plants. X. campestris has been genetically engineered to use whey as
source of carbon for production of Xanthan.
Genetically engineered X. campestris produces 4241mcg/ml of xanthan using
whey while its wild type produced only 224 mcg/ml of Xanthan with whey as a substrate.
It is used as a gelling and stabilising agent in salad dressings, ice creams, toothpastes,
cosmetics, water-based paints, etc., and also as a drilling lubricant in oil wells. The gum
itself is colourless. Xanthan is possibly the 'benchmark' product, which has gained
approval for food use many years ago. It is a relatively inexpensive product because of
the very high potential conversion of substrate to polymer. Glucose, Sucrose, Starch
may also be used as carbon sources.
Production
Xanthan gum is produced by aerobic submerged fermentation using the
bacterium Xanthomonas campestris, a micro-organism which is found naturally on
cabbages.
The polysaccharide is prepared by inoculating a sterile aqueous solution of
carbohydrate(s), a source of nitrogen, K2HPO4, and some trace elements. The medium
is well-aerated and stirred, and the polymer is produced extracellularly into the medium.
The final concentration of Xanthan produced is about three to five percent by weight.
After fermentation over about four days, the polymer is precipitated from the medium by
the addition of isopropyl alcohol and dried and milled to give a powder that is readily
soluble in water or brine.
Xanthan gum is produced commercially in conventional batch process which
runs for 80 hours. Temperature of fermentation is 280
C. As the fermentation progresses
pH drops because Xanthan gum contains acidic functional groups. If pH is less than 5
gum production tails off. When fermentation is terminated broth is at pH 6 and viscosity

32
is >30,000 cP 250
C and 1s-1
. (The viscosity of water is 1 cP and that of 20% yeast
suspension is 1000 cP.) Based on stoicheometry yields of 75-80% are obtained.
However due to high viscosity gum concentration is <5%. 1% Xanthan gum has viscosity
of 1000 cP (at pH 1-13 and 50-2000
C). Product recovery starts with pasteurization of
broth to kill bacteria. Cells may be digested enzymatically and then drum-drying or
spray-drying of fermentation liquor yields crude product. Other grades can be obtained
by precipitation with methanol or isopropanol in presence of KCl. Xanthan gum can also
be precipitated with ca+2 and then washing with acid or salt. The precipitated cake is
recovered by filtration or centrifugation followed by drying, milling and packaging. A clear
food-grade product can be obtained by diluting the fermentation liquor and clarifying by
filtration.
The gums are recovered from the fermentation broth, by addition of alcohol
(usually isopropyl alcohol) causing precipitation of Xanthan and Gellan fibers.
The resulting fibers are then treated to remove the excess alcohol and dried
under careful conditions.
The resulting "cake" is ground milled into a powder and packaged in a controlled
environment.
The final Xanthan gum and Gellan gum products are subject to extensive Quality
Control testing before being released for sale.
The yield of Xanthan is often strongly influenced by the composition of the
medium and by the nature of the growth-limiting nutrients, the highest yield being seen
under conditions of nitrogen limitation.
Looking at the conventional Xanthan production, mixing is the main problem
occurred in batch fermentation as the produced broth during the production stage is very
viscous, therefore mixing requires considerable balance between cell disruptions and
oxygen transfer. Giving the support, e.g. cotton wool and fabric, for microorganisms to
adsorb may ensure the nature physical separation between microorganisms and the
liquid phase containing nutrients and products. However, the specific Xanthan
productivity was reported low due to relatively low cell viability. The problem of the
limited oxygen transfer suggests that a new bioreactor design is required. The design
strategy could be by freely moving of the liquid media and air passing through the
porous fibrous matrix, therefore should ensure a good contact between cells that adsorb
onto the fibrous matrix support and nutrients. This strategy should improve oxygen
transfer, and may increase the reaction rate and reduce the fast growing of mutation.
Using ultrafiltration was reported save up to 80% of the energy is required for recovering
of Xanthan gum.
There is a multi-stage inoculum build up from agar plate to shake flasks to small
seed fermentation vessels to large final fermentation vessel. At all stages of production,
we have to ensure that strict aseptic techniques are followed and the culture is pure and
without contamination.
The fermentation medium is comprised of glucose syrup derived from maize or
wheat, inorganic nitrogen (ammonium or nitrate salts), an organic nitrogen source
(protein), and trace elements.
Once the final fermentation is complete, the contents of the vessel are
pasteurized to kill all the bacterial cells used in the initial culture and optimize the
conformation of the polymers.
The process diagram for both Xanthan and Gellan gums –
Fermentation – Pasteurization – Precipitation – Separation – Drying – Milling –
Packaging
Companies such as ADM and Merck have recently announced the expansion of
their Xanthan production facilities.

33
In India, Central Food Technological Research Institute (CFTRI), at Mysore has
developed technology for production of Xanthan gum and it is available for
commercialization.
Applications
About 60 percent of the Xanthan produced is used in foods, with the remaining
40 percent used in industrial applications. Food-grade Xanthan costs about $8 to $10
per pound, while non-food grades sell for about $5 per pound.
In cosmetics Xanthan gum is used to prepare water gels usually in conjunction
with bentonite clays. It is also used in oil-in-water emulsions to help stabilize the oil
droplets against coalescence. It has some skin hydrating properties.
Sr. No. Industry Applications
1 Petroleum Flocculent and lubricant
2 Textile
Suspending agent for dyes, pigments and
controlling agent in printing
3 Paints and inks Stabilizer and emulsifier for thixotropic paints
4 Ceramics Suspending agent in ceramics glazes
5 Paper and pulp
Rheology modifier for high size press and roll
coating
6
Adhesives, toothpastes
and cosmetics
Used to control viscosity and modify flow
7 Food
Used to improve texture of bread, mouth feel of
bakery products and freeze-thaw stability of frozen
foods. Used as thickening (in juice, drinks,
chocolates, and pickles) and gelling agent (in dairy)
2.8.2 Pullulan
Chemical Structure
Pullulan is produced by Aureobasidium pullulans (Black yeast). This is a glucan
gum composed of maltotriose units, and small number of maltetraoses units (1,4 
linked) which are coupled through 1,6  bonds to give linear molecule. Molecular weights
of pullulan range from thousands to 2,000,000 daltons depending on the growth
conditions of the organism Aureobasidium pullulans. The molecular mass of pullulan is
between 1 X 103
and 3 X 106
Da depending on the strains and cultivation conditions
employed..
The biopolymer pullulans with molecular weight of 10000 to 400000 is produced
in the medium containing starch or many other sugar sources. Pullulans is a natural
glucan consisting of  -maltotriose units polymerized in linear fashion through 1-6
linkage on the terminal glucose residue of trisaccharide. Maltotetrose units are also
present in some polymers.

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