Dataset Information

Cofactor recycling for co-production of 1,3-propanediol and glutamate by metabolically engineered Corynebacterium glutamicum.

ABSTRACT: Production of 1,3-propanediol (1,3-PDO) from glycerol is a promising route toward glycerol biorefinery. However, the yield of 1,3-PDO is limited due to the requirement of NADH regeneration via glycerol oxidation process, which generates large amounts of undesired byproducts. Glutamate fermentation by Corynebacterium glutamicum is an important oxidation process generating excess NADH. In this study, we proposed a novel strategy to couple the process of 1,3-PDO synthesis with glutamate production for cofactor regeneration. With the optimization of 1,3-PDO synthesis route, C. glutamicum can efficiently convert glycerol into 1,3-PDO with the yield of ~ 1.0?mol/mol glycerol. Co-production of 1,3-PDO and glutamate was also achieved which increased the yield of glutamate by 18% as compared to the control. Since 1,3-PDO and glutamate can be easily separated in downstream process, this study provides a potential green route for coupled production of 1,3-PDO and glutamate to enhance the economic viability of biorefinery process.

SUBMITTER: Huang J

PROVIDER: S-EPMC5296756 | biostudies-literature | 2017 Feb

REPOSITORIES: biostudies-literature

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Cofactor recycling for co-production of 1,3-propanediol and glutamate by metabolically engineered Corynebacterium glutamicum.

Huang Jinhai J Wu Yao Y Wu Wenjun W Zhang Ye Y Liu Dehua D Chen Zhen Z

Scientific reports 20170208

Production of 1,3-propanediol (1,3-PDO) from glycerol is a promising route toward glycerol biorefinery. However, the yield of 1,3-PDO is limited due to the requirement of NADH regeneration via glycerol oxidation process, which generates large amounts of undesired byproducts. Glutamate fermentation by Corynebacterium glutamicum is an important oxidation process generating excess NADH. In this study, we proposed a novel strategy to couple the process of 1,3-PDO synthesis with glutamate production ...[more]

PMID: 28176878

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Project description:?-D-Glucosylglycerol (?GG) has beneficial functions as a moisturizing agent in cosmetics and potential as a health food material, and therapeutic agent. ?GG serves as compatible solute in various halotolerant cyanobacteria such as Synechocystis sp. PCC 6803, which synthesizes ?GG in a two-step reaction: The enzymatic condensation of ADP-glucose and glycerol 3-phosphate by GG-phosphate synthase (GGPS) is followed by the dephosphorylation of the intermediate by the GG-phosphate phosphatase (GGPP). The Gram-positive Corynebacterium glutamicum, an industrial workhorse for amino acid production, does not utilize ?GG as a substrate and was therefore chosen for the development of a heterologous microbial production platform for ?GG.Plasmid-bound expression of ggpS and ggpP from Synechocystis sp. PCC 6803 enabled ?GG synthesis exclusively in osmotically stressed cells of C. glutamicum (pEKEx2-ggpSP), which is probably due to the unique intrinsic control mechanism of GGPS activity in response to intracellular ion concentrations. C. glutamicum was then engineered to optimize precursor supply for ?GG production: The precursor for ?GG synthesis ADP-glucose gets metabolized by both the glgA encoded glycogen synthase and the otsA encoded trehalose-6-phosphate synthase. Upon deletion of both genes the ?GG concentration in culture supernatants was increased from 0.5 mM in C. glutamicum (pEKEx3-ggpSP) to 2.9 mM in C. glutamicum ?otsA IMglgA (pEKEx3-ggpSP). Upon nitrogen limitation, which inhibits synthesis of amino acids as compatible solutes, C. glutamicum ?otsA IMglgA (pEKEx3-ggpSP) produced more than 10 mM ?GG (about 2 g L-1).Corynebacterium glutamicum can be engineered as efficient platform for the production of the compatible solute ?GG. Redirection of carbon flux towards ?GG synthesis by elimination of the competing pathways for glycogen and trehalose synthesis as well as optimization of nitrogen supply is an efficient strategy to further optimize production of ?GG.

Project description:Besides metabolic pathways and regulatory networks, transport systems are also pivotal for cellular metabolism and hyperproduction of biochemicals using microbial cell factories. The identification and characterization of transporters are therefore of great significance for the understanding and engineering of transport reactions. Herein, a novel l-glutamate exporter, MscCG2, which exists extensively in Corynebacterium glutamicum strains but is distinct from the only known l-glutamate exporter, MscCG, was discovered in an industrial l-glutamate-producing C. glutamicum strain. MscCG2 was predicted to possess three transmembrane helices in the N-terminal region and located in the cytoplasmic membrane, which are typical structural characteristics of the mechanosensitive channel of small conductance. MscCG2 has a low amino acid sequence identity (23%) to MscCG and evolved separately from MscCG with four transmembrane helices. Despite the considerable differences between MscCG2 and MscCG in sequence and structure, gene deletion and complementation confirmed that MscCG2 also functioned as an l-glutamate exporter and an osmotic safety valve in C. glutamicum Besides, transcriptional analysis showed that MscCG2 and MscCG genes were transcribed in similar patterns and not induced by l-glutamate-producing conditions. It was also demonstrated that MscCG2-mediated l-glutamate excretion was activated by biotin limitation or penicillin treatment and that constitutive l-glutamate excretion was triggered by a gain-of-function mutation of MscCG2 (A151V). Discovery of MscCG2 will enrich the understanding of bacterial amino acid transport and provide additional targets for exporter engineering.IMPORTANCE The exchange of matter, energy, and information with surroundings is fundamental for cellular metabolism. Therefore, studying transport systems that are essential for these processes is of great significance. Besides, transport systems of bacterial cells are usually related to product excretion as well as product reuptake, making transporter engineering a useful strategy for strain improvement. The significance of our research is in identifying and characterizing a novel l-glutamate exporter from the industrial workhorse Corynebacterium glutamicum, which will enrich the understanding of l-glutamate excretion and provide a new target for studying bacterial amino acid transport and engineering transport reactions.

Dataset Information

Cofactor recycling for co-production of 1,3-propanediol and glutamate by metabolically engineered Corynebacterium glutamicum.

Publications

Cofactor recycling for co-production of 1,3-propanediol and glutamate by metabolically engineered Corynebacterium glutamicum.

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