Solvent Control of Enzyme Selectivity

In addition to AOT-based microemulsions, a nonionic reverse micelle (GGDE/TX-100), containing a functional nonionic surfactant N-gluconyl glutamic acid didecyl ester (GGDE) and Triton X-100 (TX-lOO), was evaluated as a good alternative in which YADH exhibits higher catalytic activity and stability [89]. 

Pichia glucozyma-mediated reduction of benzil in aqueous media produced a 35 65 mixture of R,R)- and (R,S)-hydrobenzoin with transient formation of (S)-benzoin. The reduction stage can be controlled by medium engineering in a two-liquid-phase system composed of water and n-heptane (1 1), benzoin was obtained in high yield and with excellent enantiomeric excess and was prevented 

Numerous studies have demonstrated the solvent influence on enzyme enan-tioselectivity, and sometimes the enantiopreference may even be reversed by medium engineering. For instance, the enantioselectivity of asymmetric reduction of prochiral ketones catalyzed by T. ethanolicus ADH can be controlled by changing the reaction medium containing either organic solvents or ionic liquids [93]. Reversal of the enantioselectivity was reported for S. cerevisiae-catalyzed reduction of hydrophobic phenyl w-propyl ketone by means of the 

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