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( S)-4-Chloro-3-hydroxybutyronitrile [( S)-CHBN] was used as a chiral building block for the preparation of atorvastatin. In this study, ( R, S)-epichlorohydrin [( R, S)-ECH] and 1,3-dichloro-2-propanol (1,3-DCP) were investigated to prepare ( S)-CHBN by using the halohydrin dehalogenase HheC from Agrobacterium radiobacter AD1. Preparing ( S)-CHBN from ( R, S)-ECH gave a modest enantiomeric excess ( ee), whereas by using 1,3-DCP as the substrate, ( S)-CHBN was obtained with 97.3 % ee after pH optimization. However, a low ee value and low yield of ( S)-CHBN were obtained if the substrate concentration was increased to 10 g L−1. To obtain a higher ee value and yield, 16 mutants were constructed and screened. The variant W249F with improvements in activity and enantioselectivity was identified and applied at a 1,3-DCP loading of 10 g L−1, which gave ( S)-CHBN in 86 % yield with 97.5 % ee in 1 h. This is the first report of a one-step biocatalytic process for the preparation of ( S)-CHBN from prochiral 1,3-DCP. [ABSTRACT FROM AUTHOR]

( S)-4-chloro-3-hydroxybutanoate (( S)-CHBE) is an important chiral intermediate to synthesize the side chain of cholesterol-lowering drug atorvastatin. To biosynthesize the ( S)-CHBE, a recombinant Escherichia coli harboring the carbonyl reductase and glucose dehydrogenase was successfully constructed. The recombinant E. coli was cultured in a 500-L fermentor; after induction and expression, the enzyme activity and cell biomass were increased to 23,661.65 U/L and 13.90 g DCW/L which was 3.24 and 2.60-folds compared with those in the 50 L fermentor. The biocatalytic process for the synthesis of ( S)-CHBE in an aqueous-organic solvent system was constructed and optimized with a substrate fed-batch strategy. The ethyl 4-chloro-3-oxobutanoate concentration reached to 1.7 M, and the ( S)-CHBE with yield of 97.2 % and enantiomeric excess ( e.e.) of 99 % was obtained after 4-h reaction in a 50-L reactor. In this study, the space-time yield and space-time yield per gram of biomass (dry cell weight, DCW) were 413.17 mM/h and 27.55 mM/h/g DCW for ( S)-CHBE production, respectively, which were the highest values as compared to previous reports. Finally, ( S)-CHBE was extracted from the reaction mixture with 82 % of yield and 95 % of purity. This study paved the foundation for the upscale production of ( S)-CHBE by biocatalysis method. [ABSTRACT FROM AUTHOR]