(64f) Enantioselective Bioreduction of Ketone with Cofactor Recycling by the Use of Coupled Permeabilized Microorganisms

Biocatalytic oxidoreductions are key reactions for asymmetric syntheses of enantiopure compounds that are useful synthons and pharmaceutical intermediates. One of the challenges in the practical application of these reactions is the efficient recycling of the expensive nicotinamide cofactor NAD(P)H/NAD(P)+ which is often required in stoichiometric amount. We recently developed a novel cofactor recycling method for bioreduction based on the use of permeabilized microbial cells.[1-2] By using permeabilized cells of Bacillus pumilus Phe-C3 containing an enantioselective ketoreductase and a glucose-6-phosphate dehydrogenase as catalysts, bioreduction of ethyl 3-keto-4,4,4-trifluoro-butyrate in the presence of glucose-6-phosphate and trace amounts of NADP+ gave (R)-ethyl 3-hydroxy-4,4,4-trifluorobutyrate in 95% ee with NADPH recycling for 4200 times.[1] In a more general approach, permeabilized cells of B. pumilus Phe-C3 containing the ketoreductase were coupled with permeabilized cells of Bacillus subtilis BGSC 1A1 containing a glucose dehydrogenase (GDH), in the presence of glucose and trace amounts of NADP+, for the bioreduction of the 3-ketoester, giving rise to the recycling of NADPH for 1620 times.[2] To further improve the cofactor recycling in this general approach, we have been working on the development of highly active recombinant strain expressing GDH, the optimization of the permeabilization conditions for the cofactor-regenerating microorganisms, the optimal coupling of two permeabilized microorganisms for the bioreduction to achieve much higher turn over number of the cofactor recycling, and the long-term utilization of the permeabilized cells couple for biotransformation. Our recent progress will be presented.

REFERENCES:

[1]Zhang, J.; Witholt, B.; Li, Z. Adv. Syn. Catal. 2006, 348, 429-433.

[2]Zhang, J.; Witholt, B.; Li, Z. Chem. Commun. 2006, 398-400.