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 coil 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. (C) 2012 Elsevier Inc. All rights reserved

Polyhydroxyalkanoates production from cellulose hydrolysate in Escherichia coli LS5218 with superior resistance to 5-hydroxymethylfurfural

Poly[3-hydroxybutyrate-co-3-hydroxyvalerate(3HV)] was produced in recombinant Escherichia coil LS5218 from the ruthenium-catalyzed cellulose hydrolysate and propionate. The strain was found to be resistant to 5-hydroxymethylfurfural (5-HMF), which is a major inhibitory byproduct generated in the cellulose hydrolysis reaction. The 3HV fraction was successfully regulated in the range of 5.6-40 mol%

One-Pot Microbial Production, Mechanical Properties, and Enzymatic Degradation of Isotactic P[(<i>R</i>)‑2-hydroxybutyrate] and Its Copolymer with (<i>R</i>)‑Lactate

P­[(<i>R</i>)-2-hydroxybutyrate] [P­((<i>R</i>)-2HB)] is an aliphatic polyester analogous to poly­(lactic acid) (PLA). However, little has been known for its properties because of a high cost of commercially available chiral 2HB as a starting substance for chemical polymer synthesis. In this study, P­[(<i>R</i>)-2HB] and P­[(<i>R</i>)-2HB-<i>co</i>-(<i>R</i>)-lactate] [P­((<i>R</i>)-2HB-<i>co</i>-(<i>R</i>)-LA)] with a new monomer combination were successfully synthesized in recombinant Escherichia coli LS5218 from less-expensive racemic 2HB using an <i>R</i>-specific polyester synthase. The cells expressing an engineered polyhydroxyalkanoate synthase from Pseudomonas sp. 61-3 and propionyl-CoA transferase from Megasphaera elsdenii were grown on LB medium containing 2HB and glucose in a shake flask and accumulated up to 17 wt % of P­[(<i>R</i>)-2HB] with optical purity of >99.1%. In addition, the same cells cultured in a jar-fermentor produced P­(86 mol % 2HB-<i>co</i>-LA) copolymer. Notably, the molecular weights (<i>M</i>_w) of P­(2HB) (27000) and P­(2HB-<i>co</i>-LA) (39000) were 2- and 3-fold higher than that of P­(2HB) previously synthesized by chemical polycondensation. P­(2HB) was processed into a transparent film by solvent-casting and it had flexible properties with elongation at break of 173%, which was contrast to the rigid PLA. Regarding mechanical properties, P­(2HB-<i>co</i>-LA) was tougher but less stretchy than P­(2HB). These results demonstrated that P­(2HB) has useful properties and LA units in 2HB-based polymers can act as a controllable modulator of the material properties. In addition, P­[(<i>R</i>)-2HB] was efficiently degraded by treatment of Novozym 42044 (lipase) but not Savinase 16L (protease), indicating that the degrading behavior of the polymer was similar to that of P­[(<i>R</i>)-LA]