A novel NADH-dependent carbonyl reductase from Kluyveromyces aestuarii and comparison of NADH-regeneration system for the synthesis of ethyl (S)-4-chloro-3-hydroxybutanoate

To compare NADH-regeneration systems for the synthesis of (S)-4-chloro-3-hydroxybutanoate (ECHB), a novel NADH-dependent carbonyl reductase (KaCR1), which reduced ethyl 4-chloroacetoacetate (ECAA) to form (S)-ECHB, was screened and purified from Kluyveromyces aestuarii and a gene encoding KaCR1 was cloned. Glucose dehydrogenase (GDH) and formate dehydrogenase (FDH) were compared as enzymes for NADH regeneration using Escherichia coli cells co-expressing each enzyme with KaCR1. E. coli cells coexpressing GDH produced 45.6g/l of (S)-ECHB from 50g/l of ECAA and E. coli cells coexpressing FDH, alternatively, produced only 19.0g/l. The low productivity in the case of FDH was suggested to result from the low activity and instability of FDH.