Optimizing Escherichia Coli for Carbonyl reduction

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Chiral alcohols are key intermediates in a wide variety of pharmaceutical, agrochemical and bulk chemical products. An optimized platform for using enzymes to synthesize chiral alcohols in high yield and stereochemical purity would have high utility for the production of pharmaceuticals. Whole cells of engineered Escherichia coli are particularly convenient for producing chiral alcohols by asymmetric ketone reduction. The cells provide both enzyme and reduced nicotinamide cofactors (NADH and NADPH) in a simple-to-use package. However, the presence of the endogenous beta-keto ester reductase in E. coli complicates efforts to use E. coli cells as overexpression hosts for heterologous carbonyl reductases, especially when the stereoselectivity of the heterologous enzymes doesn't match that of the E. coli activity. We have isolated the major E. coli beta-keto ester reductase and shown that it is encoded by the yqhE gene. A strain in which the yqhE gone is knocked out will be created. The engineered E. coli will be used as host to express ketoreductases, which BioCatalytics has a group of 10 with broad substrate range. One of the ketoreductase expressed in this engineered E. coli host will be used as whole cell catalyst to demonstrate the commercial potential of this strain by producing a 100 g of (S)-ethyl 4-chloro-3-hydroxybutyrate, a key intermediate for anti-cholesterol drug Lipitor.