BAKERS-YEAST MEDIATED BIOREDUCTION - PRACTICAL PROCEDURE USING ETOH AS ENERGY-SOURCE

Baker's yeast mediated bioreduction of prochiral ketones was investigated with respect to its energy source. The rate of glucose consumption was five times that of the reduction of ethyl acetoacetate (EA), and the reduction of EA proceeded under aerobic condition after glucose had been consumed. From these results, reduction by baker's yeast based on the regeneration system for NAD (P) H through the oxidative pathway of ethyl alcohol (EtOH) was developed. Under anaerobic conditions, reduction by the new procedure did not occur. The optimum conditions of EtOH concentration and temperature were about 200 mM and 30-degrees-C, respectively. At higher than 400 mM EtOH concentration, the reduction soon leveled off. The rate of EtOH consumption was less than twice that of EA reduction, and no by-products except for carbon dioxide were detected, so the new procedure is a practical one.