2. INTRODUCTION Environmental biotechnology is biotechnology that is applied to and used
to study the natural environment. Environmental biotechnology could also
imply that one try to harness biological process for commercial uses and
exploitation. The International Society for Environmental Biotechnology
defines environmental biotechnology as "the development, use and regulation
of biological systems for remediation of contaminated environments (land, air,
water), and for environment-friendly processes (green manufacturing
technologies and sustainable development).
BIOACCUMULATION
BIODEGRADATION
BIOREMEDIATI
ON BIOLEACHINGBIOMETHANATIO
3. BIOACCUMULATION
Bioaccumulation refers to the accumulation of substances, such as pesticides,
or other organic chemicals in an organism. Bioaccumulation occurs when an
organism absorbs a toxic substance at a rate greater than that at which the
substance is lost. Thus, the longer the biological half-life of the substance the
greater the risk of chronic poisoning, even if environmental levels of the toxin
are not very high. Bioaccumulation, for example in fish, can be predicted by
models.Biotransformation can strongly modify bioaccumulation of chemicals
in an organism.
BIOACCUMULATION is result of three processes:
1)uptake
2)storage
3)elimination
4. BIOCONCENTRATION &
BIOMAGNIFICATION
Bioconcentration is a related but more specific term, referring to
uptake and accumulation of a substance from water alone. By contrast,
bioaccumulation refers to uptake from all sources combined (e.g.
water, food, air, etc.)
Biomagnification, also known as bioamplification or biological
magnification, is the increase in concentration of a substance that
occurs in a food chain as a consequence of:
Persistence (can't be broken down by environmental processes)
Food chain energetic
Low (or nonexistent) rate of internal degradation/excretion of the
substance (often due to water-insolubility)
6. BIODEGRADATION
Biodegradation is the chemical dissolution of materials by
bacteria or other biological means. Although often conflated,
biodegradable is distinct in meaning from compostable. While
biodegradable simply means to be consumed by microorganisms
and return to compounds found in nature, "compostable" makes
the specific demand that the object break down in a compost
pile. The term is often used in relation to ecology, waste
management, biomedicine, and the natural environment
(bioremediation) and is now commonly associated with
environmentally friendly products that are capable of decomposing
back into natural elements. Organic material can be degraded
aerobically with oxygen, or anaerobically, without oxygen.
Biosurfactant, an extracellular surfactant secreted by
microorganisms, enhances the biodegradation process.
7. Co-metabolism
Co-metabolism is defined as the simultaneous
degradation of two compounds, in which the degradation
of the second compound (the secondary substrate)
depends on the presence of the first compound (the
primary substrate). For example, in the process of
metabolizing methane, propane or simple sugars, some
bacteria, such as Pseudomonas stutzeri OX1, can degrade
hazardous chlorinated solvents, such as
tetrachloroethylene and trichloroethylene, that they would
otherwise be unable to attack. They do this by producing
the methane monooxygenase, enzyme which is known to
degrade some pollutants, such as chlorinated solvents, via
co-metabolism. Co-metabolism is thus used as an
approach to biological degradation of hazardous solvents.
8. BIOREMEDIATION Bioremediation is the use of micro-organism metabolism to remove
pollutants. Technologies can be generally classified as in situ or ex situ.
In situ bioremediation involves treating the contaminated material at
the site, while ex situ involves the removal of the contaminated
material to be treated elsewhere. Some examples of bioremediation
related technologies are phytoremediation, bioventing, bioleaching,
landfarming, bioreactor, composting, bioaugmentation, rhizofiltration,
and biostimulation.
10. BIOLEACHING
Bioleaching is the extraction of metals from their
ores through the use of living organisms. This is much
cleaner than the traditional hea leaching using
cyanide. Bioleaching is one of several applications
within biohydrometallurgy and several methods are
used to recover copper, zinc, lead, arsenic, antimony,
nickel, molybdenum, gold, silver, and cobalt.
11. Process Of Bioleaching
Bioleaching can involve numerous ferrous iron and sulfur
oxidizing bacteria, including Acidithiobacillus ferrooxidans and
Acidithiobacillus (formerly known as Thiobacillus). As a general
principle, Fe3+ ions are used to oxidize the ore. This step is
entirely independent of microbes. The role of the bacteria is the
further oxidation of the ore, but also the regeneration of the
chemical oxidant Fe3+ from Fe2+. For example, bacteria catalyse
the breakdown of the mineral pyrite (FeS2) by oxidising the
sulfur and metal (in this case ferrous iron, (Fe2+)) using oxygen .
This yields soluble products that can be further purified and
refined to yield the desired metal.
Pyrite leaching (FeS2): In the first step, disulfide is
spontaneously oxidized to thiosulfate by ferric ion (Fe3+), which
in turn is reduced to give ferrous ion (Fe2+):
12. Process Of Bioleaching
(1) spontaneous The ferrous ion is then oxidized by bacteria using oxygen:
(2) (iron oxidizers) Thiosulfate is also oxidized by bacteria to give sulfate:
(3) (sulfur oxidizers) The ferric ion produced in reaction (2) oxidized more
sulfide as in reaction (1), closing the cycle and given the net reaction:
(4) The net products of the reaction are soluble ferrous sulfate and sulfuric
acid.
The microbial oxidation process occurs at the cell membraneof the
bacteria. The electrons pass into the cells and are used in biochemical
processes to produce energy for the bacteria while reducing oxygen to water
The critical reaction is the oxidation of sulfide by ferric iron. The main role of
the bacterial step is the regeneration of this reactant.
The process for copper is very similar, but the efficiency and kinetics depend
on the copper mineralogy. The most efficient minerals are supergene minerals
such as chalcocite Cu2S and covellite,CuS. The main copper mineral
chalcopyrite CuFeS2) is not leached very efficiently, which is why the dominant
copper-producing technology remains flotation, followed by smelting and
refining. The leaching of CuFeS2 follows the two stages of being dissolved and
then further oxidised, with Cu2+ ions being left in solution.
13. BIOMETHANATION
Biomethanation is the formation of methane by
microbes known as methanogens. Organisms capable
of producing methane have been identified only from
the domain Archaea, a group phylogenetically distinct
from both eukaryotes and bacteria, although many live
in close association with anaerobic bacteria. The
production of methane is an important and
widespread form of microbial metabolism. In most
environments, it is the final step in the decomposition
of biomass.
