Whole-cell biotransformation systems for reduction of prochiral carbonyl compounds to chiral alcohol in Escherichia coli.

Lactobacillus brevis alcohol dehydrogenase (Lb-ADH) catalyzes reduction of prochiral carbonyl compounds to chiral alcohol and meanwhile consumes its cofactor NADH into NAD(+), while the cofactor regeneration can be catalyzed by Candida boidinii formate dehydrogenase (Cb-FDH). This work presents three different Escherichia coli whole-cell biocatalyst systems expressing recombinant ADH/FDH, FDH-LIN1-ADH and FDH-LIN2-ADH, respectively, all of which display very high efficacies of prochiral carbonyl conversion with respect to conversion rates and enantiomeric excess values. ADH/FDH represents co-expression of Lb-ADH and Cb-FDH under different promoters in a single vector. Fusion of Lb-ADH and Cb-FDH by a linker peptide LIN1 (GGGGS)₂ or LIN2 (EAAAK)₂ generates the two bifunctional enzymes FDH-LIN1-ADH and FDH-LIN2-ADH, which enable efficient asymmetric reduction of prochiral ketones in whole-cell biotransformation.