Poly(4-Hydroxybutyrate): Current State and Perspectives.

By the end of 1980s, for the first time polyhydroxyalkanoate (PHA) copolymers with incorporated 4-hydroxybutyrate (4HB) units were produced in the bacterium (formally ) from structurally related carbon sources. After that, production of PHA copolymers composed of 3-hydroxybutyrate (3HB) and 4HB [P(3HB--4HB)] was demonstrated in diverse wild-type bacteria. The P4HB homopolymer, however, was hardly synthesized because existing bacterial metabolism on 4HB precursors also generate and incorporate 3HB.

Influence of Unusual Co-substrates on the Biosynthesis of Medium-Chain-Length Polyhydroxyalkanoates Produced in Multistage Chemostat.

A two-stage chemostat cultivation was used to investigate the biosynthesis of functionalized medium-chain-length polyhydroxyalkanoate (mcl-PHA) in the β-oxidation weakened strain of KTQQ20. Chemostats were linked in sequence and allowed separation of biomass production in the first stage from the PHA synthesis in the second stage. Four parallel reactors in the second stage provided identical growth conditions and ensured that the only variable was the ratio of decanoic acid (C10) to an unusual PHA monomer precursor, such as 10-undecenoic acid (C11:1) or phenylvaleric acid (PhVA).

Tailored biosynthesis of polyhydroxyalkanoates in chemostat cultures.

Polyhydroxyalkanoates (PHAs) are accumulated intracellularly by many bacteria and serve as a carbon and energy storage compound. PHAs are polyesters of high molecular weight and can be isolated by solvent extraction and precipitation in antisolvents. The material properties of PHAs are of great interest due to the inherent biodegradability and excellent biocompatibility.

In Vitro Analysis of d-Lactyl-CoA-Polymerizing Polyhydroxyalkanoate Synthase in Polylactate and Poly(lactate- co-3-hydroxybutyrate) Syntheses.

Engineered d-lactyl-coenzyme A (LA-CoA)-polymerizing polyhydroxyalkanoate synthase (PhaC1STQK) efficiently produces poly(lactate- co-3-hydroxybutyrate) [P(LA- co-3HB]) copolymer in recombinant Escherichia coli, while synthesizing tiny amounts of poly(lactate) (PLA)-like polymers in recombinant Corynebacterium glutamicum. To elucidate the mechanisms underlying the interesting phenomena, in vitro analysis of PhaC1STQK was performed using homo- and copolymerization conditions of LA-CoA and 3-hydroxybutyryl-CoA. PhaC1STQK polymerized LA-CoA as a sole substrate.

Investigation of the Escherichia coli membrane transporters involved in the secretion of d-lactate-based oligomers by loss-of-function screening.

d-Lactate (LA)-based oligomers (D-LAOs) are unusual oligoesters consisting of d-LA and d-3-hydroxybutyrate that are produced and secreted by engineered Escherichia coli grown on glucose. The cells heterologously express LA-polymerizing polyhydroxyalkanoate synthase and monomer-supplying enzymes. In this study, we attempted to identify the D-LAO secretion route in E.

Microbial secretion of lactate-enriched oligomers for efficient conversion into lactide: A biological shortcut to polylactide.

Recently, we have succeeded in establishing the microbial platform for the secretion of lactate (LA)-based oligomers (D-LAOs), which consist of D-LA and d-3-hydroxybutyrate (d-3HB). The secretory production of D-LAOs was substantially enhanced by the supplementation of diethylene glycol (DEG), which resulted in the generation of DEG-capped oligomers at the carboxyl terminal (referred as D-LAOs-DEG). The microbial D-LAOs should be key compounds for the synthesis of lactide, an important intermediate for polylactides (PLAs) production, eliminating the costly chemo-oligomerization step in the PLA production process.

Microbial production of poly(lactate-co-3-hydroxybutyrate) from hybrid Miscanthus-derived sugars.

P[(R)-lactate-co-(R)-3-hydroxybutyrate] [P(LA-co-3HB)] was produced in engineered Escherichia coli using lignocellulose-derived hydrolysates from Miscanthus × giganteus (hybrid Miscanthus) and rice straw. Hybrid Miscanthus-derived hydrolysate exhibited no negative effect on polymer production, LA fraction, and molecular weight of the polymer, whereas rice straw-derived hydrolysate reduced LA fraction. These results revealed that P(LA-co-3HB) was successfully produced from hybrid Miscanthus-derived sugars.