NADPH-dependent reduction of ethyl acetoacetate coupled with ethanol oxidation in Kloeckera magna

We evaluated the catalytic ability of 29 yeast strains to reduce ethyl acetoacetate (EA) in the presence of ethanol or glucose. In 18 yeast strains, the reduction in the presence of ethanol proceeded as well as in the presence of glucose. Among them, Kloeckera magna (AKU 4704) effectively catalyzed the NADPH-dependent reduction of EA in the presence of ethanol. In this reduction, 1 mol of EA was reduced by consuming 1 mol of ethanol. We found that the NADPH regeneration system responsible for EA reduction in K. magna was coupled with oxidation of acetaldehyde to acetic acid catalyzed by an NADP(+)-dependent aldehyde dehydrogenase.