Research paperEnhancement of ethyl (S)-4-chloro-3-hydroxybutanoate production at high substrate concentration by in situ resin adsorption

- A carbonyl reductase was discovered to reduce COBE to (S)-CHBE with high activity.
- A cofactor regeneration system was built by coexpressing two genes in E. coli.
- The product (S)-CHBE was the main inhibitor for the reaction.
- In situ adsorption of (S)-CHBE by resin HZ 814 was used to avoid this inhibition.
- COBE at 3000 mM was completely reduced to (S)-CHBE (>99% ee) within 8 h.

Asymmetric reduction of ethyl 4-chloro-3-oxobutyrate (COBE) by carbonyl reductases presents an efficient way to produce Ethyl (S)-4-chloro-3-hydroxybutanoate ((S)-CHBE), an important chiral intermediate for the synthesis of hydroxymethylglutaryl-CoA reductase inhibitors such as Lipitor®. In this study, an NADPH-dependent carbonyl reductase (SrCR) from Synechocystis sp. was characterized to demonstrate a broad substrate spectrum, and the highest activity (53.1 U/mg protein) with COBE. To regenerate the cofactor NADPH, Bacillus subtilis glucose dehydrogenase was successfully coexpressed with SrCR. Owing to the product inhibition, no more than 400 mM of COBE could be completely reduced to (S)-CHBE using the recombinant Escherichia coli/pET-SrCR-GDH. The macroporous adsorption resin HZ 814 was applied to adsorb (S)-CHBE in situ to alleviate the product inhibitio. Consequently, 3000 mM (494 g/L) of COBE was bioconverted within 8 h, resulting in a (S)-CHBE yield of 98.2%, with 99.4% ee and total turnover number of 15,000, revealed great industrial potential of (S)-CHBE production.