Microorganisms transfer from operators

Fermentation processes, except for sterilization, have in common many of the familiar chemical engineering unit operations. For example, aerobic fermentations involve the mixing of three heterogeneous phases microorganisms, medium, and air. Other unit operations include mass transfer of oxygen from the air to the organisms and heat transfer from the fermentation medium. 

Figure 17.1 Sequence of events in the overall process of biotrans-formations (1) bacterial cell containing enzymes takes up organic chemical, /, (2) i binds to suitable enzyme, (3) enzyme / complex reacts, producing the transformation product(s) of /, and (4) the product(s) is(are) released from the enzyme. Several additional processes may influence the overall rate such as (5) transport of / from forms that are unavailable (e.g., sorbed) to the microorganisms, (6) production of new or additional enzyme capacity [e.g., due to turning on genes (induction), due to removing materials which prevent enzyme operation (activation), or due to acquisition of new genetic capabilities via mutation or plasmid transfer], and (7) growth of the total microbial population carrying out the biotransformation of /. ...

It should be noted that PBRs operate differently than other gas-Uquid reactors covered so far. In the other reactor designs, the gas phase is dispersed in the liquid phase such that bubbles are formed from which the gas phase is transferred to the liquid. The surface area through which the transfer occurs is the interfacial area of the bubbles. In PBRs, general operation yields droplets or liquid films immersed in the gas phase, which causes the main transfer surface to be the droplet-gas or film-gas interface. In order to increase the mass transfer interiacial area, smaUer droplets or wavier films have to be produced. This process is often turbulent and may result in liquid breakup and coalescence, which may be destractive to some microorganisms (specifically those that are shear sensitive). 

Figure 2.1. Procedure for transferring the biocatalytic characteristics of microorganisms from the laboratory to an industrial-scale operation. (Adapted from Aiba, Humphrey and Millis, 1976.)...

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