Efficient production of d -1,2,4-butanetriol from d -xylose by engineered Escherichia coli whole-cell biocatalysts

We have developed a whole-cell bioconversion system for the production of d -1,2,4-butanetriol (BT) from renewable biomass. A plasmid pETduet- xylB - yjhG -T7- adhP -T7- mdlC was constructed and transformed to Escherichia coli BL21(DE3) to obtain the whole cells of E. coli BL21- XYMA capable of bioconversion d -xylose to BT. Then, the factors including carbon sources, nitrogen sources, metal ions, and culture conditions (pH, temperature, IPTG) were identified, and their effects on the whole-cell activity for BT production were investigated. To obtain the highest whole-cell activity, the optimal cultivation parameters are: 15 g·L –1 yeast extract, 5 g·L –1 sucrose, 3 g·L –1 KH 2 PO 4 , 5 g·L –1 NaCl, 3 g·L –1 NH 4 Cl, 0.25 g·L –1 MgSO 4 ·7H 2 O and 1 mL·L –1 the mixture of trace elements. With the optimized whole cells of E. coli BL21- XYMA , 60 g·L –1 of xylose was converted to 28 g·L –1 BT with a molar yield of 66 %, which is higher than those reported in the biotechnological system.