RELATIONSHIP BETWEEN ETHANOL-CONSUMPTION RATE AND PROCHIRAL KETONE REDUCTION RATE IN BAKERS-YEAST

The relationship between ethanol consumption and the bioreduction of p rochiral ketones in bakers' yeast cells using ethanol as a reductant f or NAD(P)H regeneration was examined and the efficiency (nu(sub)/nu(Et OH)) correlated to k(L) alpha. Ethanol was consumed at almost the same specific rate in the presence or absence of the ketones. In the reduc tion of ethyl acetoacetate catalyzed by NADPH-dependent oxidoreductase , the efficiency (nu(EA)/nu(ELOH)) decreased with increasing k(L) alph a and was about 0.5 at the actual operating condition of kLa of 100 h( -1). The reduction of acetol catalyzed by NADH-dependent oxidoreductas e proceeded through the use of a portion of NADH in the regenerated NA DH, and the efficiency (nu(acetot)/nu(EtOH)) had a maximum (1.9) at k( L) alpha of 20h(-1)