Effectiveness of xylose utilization for high yield production of lactate-enriched P(lactate-co-3-hydroxybutyrate) using a lactate-overproducing strain of Escherichia coli and an evolved lactate-polymerizing enzyme

Xylose, which is a major constituent of lignocellulosic biomass, was utilized for the production of poly(lactate-co-3-hydroxybutyrate) [P(LA-co-3HB)], having transparent and flexible properties. The recombinant Escherichia coli JW0885 (pflA−) expressing LA-polymerizing enzyme (LPE) and monomer supplying enzymes grown on xylose produced a copolymer having a higher LA fraction (34 mol%) than that grown on glucose (26 mol%). This benefit of xylose was further enhanced by combining it with an evolved LPE (ST/FS/QK), achieving a copolymer production having 60 mol% LA from xylose, while glucose gave a 47 mol% LA under the same condition. The overall carbon yields from the sugars to the polymer were similar for xylose and glucose, but the ratio of the LA and 3HB units in the copolymer was different. Notably, the P(LA-co-3HB) yield from xylose (7.3 g l−1) was remarkably higher than that of P(3HB) (4.1 g l−1), indicating P(LA-co-3HB) as a potent target for xylose utilization.