초록
<P>Biocatalysis has advantages in asymmetric synthesis due to the excellent stereoselectivity of enzymes. The present study established an efficient biosynthesis pathway for optically pure (<I>S</I>)-3-hydroxy-γ-butyrolactone [(<I>S</I>)-3HγBL] production using engineered <I>Escherichia coli</I>. We mimicked the 1,2,4-butanetriol biosynthesis route and constructed a five-step pathway consisting of <SMALL>D</SMALL>-xylose dehydrogenase, <SMALL>D</SMALL>-xylonolactonase, <SMALL>D</SMALL>-xylonate dehydratase, 2-keto acid decarboxylase, and aldehyde dehydrogenase. The engineered strain harboring the five enzymes could convert <SMALL>D</SMALL>-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%. (<I>S</I>)-3HγBL production was further enhanced by disrupting the branched pathways responsible for <SMALL>D</SMALL>-xylose uptake and intermediate reduction. Fed-batch fermentation of the best engineered strain showed the highest (<I>S</I>)-3HγBL titer of 3.5 g/L. The volumetric productivity and molar yield of (<I>S</I>)-3HγBL on <SMALL>D</SMALL>-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 <SMALL>D</SMALL>-xylose as the feedstock and offered an alternative approach for the production of the valuable chemical.</P><BR>[FIG OMISSION]</BR>