Membrane bioreactors regeneration

One of the major disadvantages of using these enzymes to reduce ketones is generally the very poor aqueous solubility of the substrates (usually <5-10 mM) and the fact that the co-factor regeneration system is sensitive to organic solvents. To address this limitation, biphasic and membrane bioreactors have been used that allow for moderate to high conversions with often >99% ee for selected products. This has been demonstrated with the (.S )-Adi I from Rhodococcus erythropolis,36-37... 

Steady state models of membrane bioreactors utilizing a multi-enzyme system, which in addition to the main reaction promotes the simultaneous regeneration of the co-factor (for further discussion see Chapter 4) have been developed by different groups in Japan [5.109, 5.110]. Several of these studies have also considered the effect of backmixing [5.111, 5.112]. A model of an enzymatic hollow fiber membrane bioreactor with a single enzyme, which utilizes two different substrates (reaction 5.42) has been developed recently by Salzman et al [5.113]. 

In addition, the substrate and product should be transported through the cell membrane, either passively or actively, and necessary cofactors should be regenerated. Finally, the specific organism used should function well in an optimized bioreactor system. All of these requirements can be met by using strains that contain the desired enzyme in question. 

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