Airlift fermenter

Airlift Fermenter, 4 types , Advantages , Applications

1. Presentation by : Parnavi S. Kadam Topic : Airlift fermenter

2. Fermenter The basic function of a fermenter is to provide a controlled environment for the growth of micro-organisms or animal cells, to obtain a desired product. Points that should be considered while designing & constructing a fermenter :- 1) The fermenter should be capable of being operated aseptically for a no.of days 2) It should be reliable in long-term operation 3) Adequate aeration & agitation should be provided to meet the metabolic requirements of the microbe.Howeever mixing should not cause damage to the organism. 4) Power consumption should be as low as possible (2)

3. 5 ) Systems for temperature & pH control should be provided 6) Sampling facilities should be provided 7) The vessel should be designed to require the minimal use of labour in operation, harvesting,cleaning & maintanence . 8)The vessel should be of similar geometry to both smaller and larger vessels in the pilot plant or plant to facilitate scale-up . (3)

4. What is an Airlift Fermenter ? Air lift/Gas lift bioreactors are an alternative to mechanically agitated systems that reduce shear stress by eliminating the mechanical agitator. Types of an Airlift fermenter Concentric draft tube Airlift fermenter Tower loop Airlift fermenter ICI deep shaft Airlift fermenter Low pressure Airlift fermenter (4)

5. Airlift fermenter 1)Concentric draft tube airlift fermenter

6. Also called as ‘Airlift Fermenter with inner loop ’ Most industrial airlift fermenters are of this type It is used for continuous culture. It consists of an internal riser tube(draft tube) which is placed inside the downcomer tube . Air or gas mixtures are introduced into the base of the internal riser by a sparger during normal working conditions. The draft tube functions as the aerated section. The air which is sparged , rises the liquid(media containing nutrients and the cell mass)up and eventually it flows down in the downcomer tube. The driving force for the circulation of the medium in the vessel is produced by the difference in the density between the liquid column in the riser and the liquid column in the downcomer . (5)

7. The ratio of the diameter of the draft tube to that of the downcomer tube is one of the important design characteristics in maximizing liquid circulation rate & in minimizing mixing time. Diameter ratios in the range of 0.6-0.8 have often been quoted to give optimal performance. Baffles are incorporated in the draft tube to prevent vortex formation & to improve aeration efficiency. Cooling system is incorporated in the fermenter design by involving cooling jackets around the wall of the downcomer tube (6)

8. 2)TOWER LOOP AIRLIFT FERMENTER Tower loop airlift fermenters , also known as external loop airlift fermenters or tubular loop fermenters , differ from the concentric tube fermenters by having the air- sparged riser column physically separated from the downcomer . (7)

9. 3) ICI DEEP SHAFT AIRLIFT FERMENTER Developmental work for operational processes for SCP has been done by ICI plc in Great Britain (Taylor and Senior, 1978;Smith,1980), Hoechst AG- Unhe GmbH in Germany (Faust et al., 1977) & Mitsubishi Gas Chemical Co.Inc . in Japan( Kuraishi et al., 1978). 4) LOW PRESSURE AIRLIFT FERMENTER To produce single-cell protein from hydrocarbons, the high demand of oxygen with hydrocarbon substrates and the rising cost of energy and capital investment made it apparent that economical fermenter designs could have a significant impact on the cost of production. (8)

10. Advantages of a Airlift Fermenter Airlift fermenter is without any mechanical stirring arrangements Turbulence caused by fluid flow ensures adequate mixing of the liquid Compared to stirred tank airlift’s are easy to scale up & they require less energy to operate It is ideally suited for aerobic cultures since oxygen mass transfer coefficient are quite high. Applications: Production of beer,yeast & SCP Waste water treatment To produce biopharma proteins from fragile cells (9)

11. References Stanburry P.F,Whittaker A,Hall S.J,Principles of Fermentation Technology,2ⁿᵈ Edition N.Y. Chen (1990) The Design of Airlift Fermenters for use in Biotechnology, Biotechnology and Genetic Engineering Reviews,8:1, 379-396, DOI:10.1080/02648725.1990.10647875

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