Continuous sterilization is the rapid transfer of heat to medium through steam condensate without the use of a heat exchanger. ... This is more efficient than batch sterilization because instead of expending energy to heat, hold, and cool the entire system, small portions of the inlet streams are heated at a time.

1. Batch and Continuous Sterilization
Sterilization of Media for Fermentation
Dr. Pavan J Kundur
Assistant Professor
P C Jabin Science College
Hubballi

2.  Batch Sterilization is the reduction of contaminant
organisms through the heating of a vessel.
The entire volume of media is sterilized at once through
the use of thermal or radiation techniques.
When running a thermal batch sterilization, a system goes
through 3 steps: heating, holding, and cooling.
Heating requires the addition of energy throughout the
entire medium volume.
This can be done by adding heat through a jacket on the
vessel.

3. The temperature is increased until it reaches the
sterilization temperature where it is held for a set period
of time.
During this phase, most of the unwanted microorganisms
are destroyed.
Finally, the system is cooled to bring the sterile media
back to the desired temperature.
For radiation sterilization, the process is similar to above,
although it uses radiation intensity instead of heat.

5. In order to sterilize a batch, calculate the total area
underneath the curve. Therefore, model death using first
order kinetics and integrate as seen above. This will yield a
temperature and the corresponding duration of time needed
to sterilize the media.
Advantages:
Most widely used technique
Simple operation
No additional materials are added to the media itself
Disadvantages:
More expensive heat requirements than continuous
sterilization
Best results occur in well-mixed closed vessels

6. Continuous Sterilization

7.  Continuous sterilization is the rapid transfer of heat to medium through steam
condensate without the use of a heat exchanger.
 Once the media is in a holding loop, steam is injected to the system via a nozzle.
The medium stays in this loop for a predetermined holding time until the entire
medium is sterile.
 This is more efficient than batch sterilization because instead of expending energy
to heat, hold, and cool the entire system, small portions of the inlet streams are
heated at a time.
 By looping sterile media tubes (which are at higher temperatures) past inlet tubes,
the difference in temperature is used to help heat the unsterile medium.
 So instead of having a cold-water stream cool the sterile media, the lower
temperature unsterile media stream absorbs heat from the warm stream, cooling the
sterile media.
 Finally, the sterile media is flash cooled through an expansion valve to adjust the
temperature to meet process parameters.

9. Advantages:
Uniform steam requirements throughout the duration of the
sterilization
Simplified process control
Shorter sterilization time means less thermal degradation of
medium
Disadvantages:
High demand for steam in a shorter period of time than batch
Concentration of media becomes dilute due to steam
condensation
Since steam is actually dispersed in media, steam must be
clean to avoid contamination

10. Advantages of Continuous
Sterilization process
over Batch Sterilization

11.  Better protection of medium value .
 Batch sterilization wastes energy and can
overcook the medium
 Batch sterilization uses steam or direct heat to
elevate the temperature. Both the heat and the
cooling water are spent with no opportunity for
energy recovery.
 temperature in batch sterilization can not increased
beyond 121°c as if the temperature is increased, the
heating & cooling period increases .
 hence during sterilization the nutrient media will be
degraded .

12.  Continuous Sterilization is the method of choice .
 In Continuous Sterilization , the medium to be sterilized
is dealt in small increments &
 hence there is shorter heating & cooling periods.
 much higher temperature can be utilized , thus reducing
holding time.
 therefore, in continuous sterilization nutrient
degradation is subsequently less as compared to batch
sterilization .
 This is more efficient than batch sterilization because
instead of expending energy to heat, hold, and cool the
entire system, small portions of the inlet streams are
heated at a time

13.  Most of the sterilization in the continuous
sterilization process may occurs in the
holding
The holding section is a long pipe,
λhold =
L
uav
length of the pipe
average fluid velocity
in the pipe

14.  High steam utilization capacity. As compared to batch
sterilization
 The heat can be fully utilized during sterilizing process
and
 therefore, great amount of water and steam can be saved
as well as energy consumption is decreased substantially.
 It can averagely save about 30% of steam and 40% of
cooling water throughout the sterilization process if
Continuous Sterilization Technology is applied.

15.  Easy Scaling-up of the process .
 On scaling up the fermentation it was very difficult to
attain the correct sterilization conditions using the batch
regime .
 Continuous sterilization using direct steam injection
allowed the design of a precise process producing sterile
medium with the required degree of interaction b/w the
ingredients .
The temperature profile of the medium allowing an easy
estimate of the Del factor (∆) required. This makes
scale-up very simple.

16.  Easier to automate the process
 The Continuous Sterilizer is not a pressure vessel and
is easy to automate the whole process .
 hence improves the quality of sterilization & reduce
labor intensive
 Reduces manpower, machinery replacement and
maintenance
 Reduction of sterilization cycle time

17. Thank You