Batch and Continuous Sterilization of Media in Fermentation Industry
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The document discusses batch and continuous sterilization methods used for fermentation media. Batch sterilization involves heating the entire volume of media at once, while continuous sterilization utilizes steam injection for rapid heating, resulting in time and energy efficiency. Continuous sterilization has advantages such as reduced nutrient degradation, easier automation, and significant savings on steam and cooling water compared to batch sterilization.
Batch and Continuous Sterilization of Media in Fermentation Industry
- 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
- 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