L-Lysine is a potential feedstock for the production of bio-based precursors for engineering plastics. In this study, we developed a microbial process for high-level conversion of L-lysine into 5-aminovalerate (5AVA) that can be used as a monomer in nylon 6,5 synthesis. Recombinant Escherichia coli WL3110 strain expressing Pseudomonas putida delta-aminovaleramidase (DavA) and lysine 2-monooxygenase (DavB) was grown to high density in fed-batch culture and used as a whole cell catalyst. High-density E. coli WL3110 expressing DavAB, grown to an optical density at 600 nm (OD600 ) of 30, yielded 36.51 g/L 5AVA from 60 g/L L-lysine in 24 h. Doubling the cell density of E. coli WL3110 improved the conversion yield to 47.96 g/L 5AVA from 60 g/L of L-lysine in 24 h. 5AVA production was further improved by doubling the L-lysine concentration from 60 to 120 g/L. The highest 5AVA titer (90.59 g/L; molar yield 0.942) was obtained from 120 g/L L-lysine by E. coli WL3110 cells grown to OD600 of 60. Finally, nylon 6,5 was synthesized by bulk polymerization of ϵ-caprolactam and δ-valerolactam prepared from microbially synthesized 5AVA. The hybrid system demonstrated here has promising possibilities for application in the development of industrial bio-nylon production processes.

The fermentative production of platform chemicals in biorefineries is a sustainable alternative to current petroleum‐refining processes. Industrial microorganisms, such as Escherichia coli, Saccharomyces cerevisiae, and Corynebacterium glutamicum, have been engineered as microbial cell factories that are able to utilize biomass for the production of value‐added platform chemicals and polymers. Compared to E. coli and S. cerevisiae, C. glutamicum displays weak carbon catabolite repression and can co‐utilize mixed sugars as carbon sources, without any significant growth retardation. Pathways for the utilization of alternative carbon sources, such as d‐xylose and l‐arabinose from lignocellulosic biomass, lactose and galactose from whey, glycerol from biodiesel, and methanol from natural gas refineries, have been evaluated for chemical production. However, the application of C. glutamicum in biorefineries is limited because it does not secrete hydrolases for the efficient utilization of cellulose, xylan, and starch from lignocellulosic and starch biomass. To solve the limitation, C. glutamicum has been engineered for the consolidated bioprocessing of biomass by the heterologous expression of amylolytic and cellulolytic enzymes. Recently, C. glutamicum has been extensively engineered for polyamide monomer production owing to its ability to produce l‐lysine and l‐glutamate. This review summarizes recent advances in the development of C. glutamicum strains that can utilize renewable biomass resources for the production of industrially important chemicals. It highlights recent progress in metabolic engineering for the production of polyamide monomers. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

Bio-based production of industrially important chemicals provides an eco-friendly alternative to current petrochemical-based processes. Because of the limited supply of fossil fuel reserves, various technologies utilizing microbial host strains for the sustainable production of platform chemicals from renewable biomass have been developed. Corynebacterium glutamicum is a non-pathogenic industrial microbial species traditionally used for L-glutamate and L-lysine production. It is a promising species for industrial production of bio-based chemicals because of its flexible metabolism that allows the utilization of a broad spectrum of carbon sources and the production of various amino acids. Classical breeding, systems, synthetic biology, and metabolic engineering approaches have been used to improve its applications, ranging from traditional amino-acid production to modern biorefinery systems for production of value-added platform chemicals. This review describes recent advances in the development of genetic engineering tools and techniques for the establishment and optimization of metabolic pathways for bio-based production of major C2-C6 platform chemicals using recombinant C. glutamicum.

BackgroundRecent interest has been focused on the production of platform chemicals from renewable biomass due to increasing concerns on global warming and depletion of fossil fuel reserves. Microbial production of platform chemicals in biorefineries has been suggested to be a promising solution for these problems. Gamma-aminobutyrate (GABA), a versatile bulk chemical used in food and pharmaceutical industry, is also used as a key monomer for nylon 4. GABA can be biologically produced by decarboxylation of glutamate.ResultsIn this study, we examined high glutamate-producing Corynebacterium glutamicum strains as hosts for enhanced production of GABA from glucose and xylose as carbon sources. An Escherichia coli gadB mutant with a broad pH range of activity and E. coli xylAB genes were expressed under the control of a synthetic H36 promoter. When empty fruit bunch (EFB) solution was used as carbon source (45 g/L glucose and 5 g/L xylose), 12.54 ± 0.07 g/L GABA was produced by recombinant C. glutamicum H36GD1852 expressing E. coli gadB mutant gene and xylAB genes. Batch fermentation of the same strain resulted in the production of 35.47 g/L of GABA when EFB solution was added to support 90 g/L glucose and 10 g/L xylose.ConclusionsThis is the first report of GABA production by recombinant C. glutamicum strains from co-utilization of glucose and xylose from EFB solution. Recombinant C. glutamicum strains developed in this study should be useful for an efficient and sustainable production of GABA from lignocellulosic biomasses.Electronic supplementary materialThe online version of this article (10.1186/s12934-018-0977-9) contains supplementary material, which is available to authorized users.

A sucrose utilization pathway was established in Ralstonia eutropha NCIMB11599 and R. eutropha 437-540 by introducing the Mannheimia succiniciproducens MBEL55E sacC gene that encodes β-fructofuranosidase. These engineered strains were examined for the production of poly(3-hydroxybutyrate) [P(3HB)] and poly(3-hydroxybutyrate-co-lactate) [P(3HB-co-LA)], respectively, from sucrose as a carbon source. It was found that β-fructofuranosidase excreted into the culture medium could hydrolyze sucrose to glucose and fructose, which were efficiently used as carbon sources by recombinant R. eutropha strains. When R. eutropha NCIMB11599 expressing the sacC gene was cultured in nitrogen-free chemically defined medium containing 20 g/L of sucrose, a high P(3HB) content of 73.2 wt% could be obtained. In addition, R. eutropha 437-540 expressing the Pseudomonas sp. MBEL 6-19 phaC1437 gene and the Clostridium propionicum pct540 gene accumulated P(3HB-co-21.5 mol% LA) to a polymer content of 19.5 wt% from sucrose by the expression of the sacC gene and the Escherichia coli ldhA gene. The molecular weights of P(3HB) and P(3HB-co-21.5 mol%LA) synthesized in R. eutropha using sucrose as a carbon source were 3.52 × 10(5) (Mn ) and 2.19 × 10(4) (Mn ), respectively. The engineered R. eutropha strains reported here will be useful for the production of polyhydroxyalkanoates (PHAs) from sucrose, one of the most abundant and relatively inexpensive carbon sources.