Efficient production of (S)-1-phenyl-1,2-ethanediol using xylan as co-substrate by a coupled multi-enzyme Escherichia coli system

Abstract

Background: (S)-1-phenyl-1,2-ethanediol is an important chiral intermediate in the synthesis of liquid crystals and chiral biphosphines. (S)-carbonyl reductase II from Candida parapsilosis catalyzes the conversion of 2-hydroxyacetophenone to (S)-1-phenyl-1,2-ethanediol with NADPH as a cofactor. Glucose dehydrogenase with a Ala258Phe mutation is able to catalyze the oxidation of xylose with concomitant reduction of NADP+ to NADPH, while endo-β-1,4-xylanase 2 catalyzes the conversion of xylan to xylose. In the present work, the Ala258Phe glucose dehydrogenase mutant and endo-β-1,4-xylanase 2 were introduced into the (S)-carbonyl reductase II-mediated chiral pathway to strengthen cofactor regeneration by using xylan as a naturally abundant co-substrate. Results: We constructed several coupled multi-enzyme systems by introducing (S)-carbonyl reductase II, the A258F glucose dehydrogenase mutant and endo-β-1,4-xylanase 2 into Escherichia coli. Different strains were produced by altering the location of the encoding genes on the plasmid. Only recombinant E. coli/pET-G-S-2 expressed all three enzymes, and this strain produced (S)-1-phenyl-1,2-ethanediol from 2-hydroxyacetophenone as a substrate and xylan as a co-substrate. The optical purity was 100% and the yield was 98.3% (6 g/L 2-HAP) under optimal conditions of 35 °C, pH 6.5 and a 2:1 substrate-co-substrate ratio. The introduction of A258F glucose dehydrogenase and endo-β-1,4-xylanase 2 into the (S)-carbonyl reductase II-mediated chiral pathway caused a 54.6% increase in yield, and simultaneously reduced the reaction time from 48 to 28 h. Conclusions: This study demonstrates efficient chiral synthesis using a pentose as a co-substrate to enhance cofactor regeneration. This provides a new approach for enantiomeric catalysis through the inclusion of naturally abundant materials.