Production of Optically Pure (S)-3-Hydroxy-γ-butyrolactone from d-Xylose Using Engineered Escherichia coli.

Abstract

Biocatalysis has advantages in asymmetric synthesis due to the excellent stereoselectivity of enzymes. The present study established an efficient biosynthesis pathway for optically pure (S)-3-hydroxy-γ-butyrolactone [(S)-3HγBL] production using engineered Escherichia coli. We mimicked the 1,2,4-butanetriol biosynthesis route and constructed a five-step pathway consisting of d-xylose dehydrogenase, d-xylonolactonase, d-xylonate dehydratase, 2-keto acid decarboxylase, and aldehyde dehydrogenase. The engineered strain harboring the five enzymes could convert d-xylose to 3HγBL with glycerol as the carbon source. Stereochemical analysis by chiral GC proved that the microbially synthesized product was a single isomer, and the enantiomeric excess (ee) value reached 99.3%. (S)-3HγBL production was further enhanced by disrupting the branched pathways responsible for d-xylose uptake and intermediate reduction. Fed-batch fermentation of the best engineered strain showed the highest (S)-3HγBL titer of 3.5 g/L. The volumetric productivity and molar yield of (S)-3HγBL on d-xylose reached 50.6 mg/(L·h) and 52.1%, respectively. The final fermentation product was extracted, purified, and confirmed by NMR. This process utilized renewable d-xylose as the feedstock and offered an alternative approach for the production of the valuable chemical.