Enhancing intracellular NADPH bioavailability through improving pentose phosphate pathway flux and its application in biocatalysis asymmetric reduction reaction.

The intracellular NAD(P)H insufficiency is the key factor which limits the reduced product (such as chiral alcohols) synthesis by whole cell biocatalysis or microbial cell factory. In this paper, we reported a novel solution to increase NADPH supply through strengthening the pentose phosphate pathway (PPP) flux with overexpression of extra zwf (gene for glucose 6-phosphatedehydrogenase) and glk (gene for glucokinase) by recombinant Escherichia coli BL21(DE3)/pETDuet-1-glk-zwf and pET28a-bccr containing a carbonyl reductase gene bccr. The amount of intracellular NADPH was significantly increased from 150.3 µmol/L to 681.8 µmol/L after strengthening the PPP flux, which was 4.5-fold to that of the control. It was applied to improve the asymmetric reduction of 4-chloroacetoacetate to ethyl S-4-chloro-3-hydroxybutylate catalyzed by the BcCR, which increased the reaction yield 2.8-fold to the control. This strategy provides a new way to increase NADPH supply in E. coli cell factories.