Novel biocatalyst for the asymmetric reduction of ketones: Permeabilized cells of Gluconobacter oxydans

Gluconobacter oxydans (ATCC 621) were permeabilized with toluene and then lyophilized. This crude enzyme preparation was used to reduce eleven ketones to (S)-alcohols with high enantiomeric excess (for most alcohols 93%-99% e.e.). The coenzyme NADH was regenerated either by adding a second enzyme, formate dehydrogenase, and its substrate, formate, or with 2-butanol as a second substrate for the G. oxydans enzyme(s). With the first of these methods, almost complete conversion was achieved. Permeabilized cells immobilized in calcium alginate gel were used for 18 days without any significant loss of catalytic activity.