The Co-Immobilization Of Short Chain Dehydrogenase/Reductase And Glucose Dehydrogenase

Chiral alcohols are key intermediate in synthesis of Chiral drugs, and biosynthesis of Chiral alcohols is a common method to get Chiral alcohols.Short-chain dehydrogenase catalyzing the biosynthesis of Chiral alcohols have the advantage of a broader range of subtratesvand good stereoselectivity, but in this reaction NAD(P)H is needed. Glucose dehydrogenase can catalyze the reduction of NAD(P)+to NAD(P)H by oxidation of glucose. It could greatly reduce the cost of NAD(P)H if short-chain dehydrogenase and glucose dehydrogenase are immobilized together in the same supporter because in this way glucose dehydrogenase was used for the NAD(P)H regeneration.The recombined short-chain dehydrogenase in this study was from the extreme hermophilic bacteria Carboxydothermus SP. Its optimum pH was in the range of6.0～6.3and its activity changed little at the range of 50℃to70℃. The half-life of the enzyme activity was7.5h at60℃The short-chain dehydrogenase can be fully and strongly absorbed on the silica-gel in1h. Stirring intensity had the great influence on the reaction of reducing ethyl phenylglyoxylate to the corresponding chiral alcohol catalyzed by immobilized short-chain dehydrogenase.Glucose dehydrogenase was from Thermoplasma acidophilum. It can regenerate NADPH for the oxi-reduction reaction catalyzed by short-chain dehydrogenase. Its optimum pH was in the range of6.5-7.5and the optimum temperature was70℃. The half-life of the enzyme activity was8h at60℃. The glucose dehydrogenase can be fully and strongly absorbed on the silica-gel (the supporter) in0.5h.Due to the similar optimum temperature and pH between the two enzymes, pH was set at6.5in the process of co-immobilization of the both enzymes. The activity of the co-immobilized short-chain dehydrogenase and glucose dehydrogenase was0.68U/mL and0.973U/mL respectively. The temperature was set at50℃when the co-immobilized enzymes was used to catalyze the reaction of chiral alcohol production.