Design of Fermenter

A bioreactor is a specially designed vessel which is built to support the growth of high concentration of microorganisms. It must be so designed that it is able to provide the optimum environments or conditions that will allow supporting the growth of the microorganisms. Bioreactors are commonly cylindrical vessels with hemispherical top and/or bottom, ranging in size from some liter to cube meters, and are often made of  stainless steel and glass. The difference between a bioreactor and a typical composting system is that more parameters of the composting process can be measured and controlled in bioreactors. The sizes of the bioreactor can vary over several orders of magnitudes. The microbial cell (few mm3 ), shake flask (100-1000 ml), laboratory fermenter (1 – 50 L), pilot scale (0.3 – 10m3 ) to plant scale (2 – 500 m3 ) are all examples of bioreactors. The design and mode of operation of a fermenter mainly depends on the production organism, the optimal operating condition required for target product formation, product value and scale of production. The design also takes into consideration the capital investment and running cost.

There are four basic components of a bioreactor including: 

1. Drive motor, heaters, pump, etc., 

2. Vessels and accessories 

3. Peripheral equipment (reagent bottles) 

4. Instrumentation and sensors 

Before designing a bioreactor following points should be considered: 

1. The vessel should be robust and strong enough to withstand the various treatments required such as exposure to high heat, pressure and strong chemicals and washings and cleanings. 

2. The vessel should be able to be sterilized and to maintain stringent aseptic conditions over long periods of the actual fermentation process. 

3. The vessel should be equipped with stirrers or mixers to ensure mass transfer processes occur efficiently. 

4. It should have sensors to monitor and control the fermentation process. 

5. It should be provided with inoculation point for aseptic transfer in inoculum.

6. Sampling valve for withdrawing a sample for different tests. 

7. Baffles should be provided in case of stirred fermenter to prevent vertex formation. 

8. It should be provided with facility for intermittent addition of an antifoam agent.

9. In case of aerobic submerged fermentation, the tank should be equipped with the aerating device. 

10. Provision for controlling temperature and pH of fermentation medium. 

11. Man hole should be provided at the top for access inside the fermenter for different purposes.