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Rewiring glycerol metabolism for enhanced production of poly-?-glutamic acid in Bacillus licheniformis.

ABSTRACT: Background:Poly-?-glutamic acid (?-PGA) is a natural polymer with great potential applications in areas of agriculture, industry, and pharmaceutical. The biodiesel-derived glycerol can be used as an attractive feedstock for ?-PGA production due to its availability and low price; however, insufficient production of ?-PGA from glycerol is limitation. Results:The metabolic pathway of Bacillus licheniformis WX-02 was rewired to improve the efficiency of glycerol assimilation and the supply of NADPH for ?-PGA synthesis. GlpK, GlpX, Zwf, and Tkt1 were found to be the key enzymes for ?-PGA synthesis using glycerol as a feedstock. Through combinational expression of these key enzymes, the ?-PGA titer increased to 19.20?±?1.57 g/L, which was 1.50-fold of that of the wild-type strain. Then, we studied the flux distributions, gene expression, and intracellular metabolites in WX-02 and the recombinant strain BC4 (over-expression of the above quadruple enzymes). Our results indicated that over-expression of the quadruple enzymes redistributed metabolic flux to ?-PGA synthesis. Furthermore, using crude glycerol as carbon source, the BC4 strain showed a high productivity of 0.38 g/L/h, and produced 18.41 g/L ?-PGA, with a high yield of 0.46 g ?-PGA/g glycerol. Conclusions:The approach to rewiring of metabolic pathways enables B. licheniformis to efficiently synthesize ?-PGA from glycerol. The ?-PGA productivity reported in this work is the highest obtained in glutamate-free medium. The present study demonstrates that the recombinant B. licheniformis strain shows significant potential to produce valuable compounds from crude glycerol.

SUBMITTER: Zhan Y

PROVIDER: S-EPMC6225680 | biostudies-other | 2018

REPOSITORIES: biostudies-other

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Rewiring glycerol metabolism for enhanced production of poly-γ-glutamic acid in <i>Bacillus licheniformis</i>.

Zhan Yangyang Y Sheng Bojie B Wang Huan H Shi Jiao J Cai Dongbo D Yi Li L Yang Shihui S Wen Zhiyou Z Ma Xin X Chen Shouwen S

Biotechnology for biofuels 20181109

<h4>Background</h4>Poly-γ-glutamic acid (γ-PGA) is a natural polymer with great potential applications in areas of agriculture, industry, and pharmaceutical. The biodiesel-derived glycerol can be used as an attractive feedstock for γ-PGA production due to its availability and low price; however, insufficient production of γ-PGA from glycerol is limitation.<h4>Results</h4>The metabolic pathway of <i>Bacillus licheniformis</i> WX-02 was rewired to improve the efficiency of glycerol assimilation an ...[more]

PMID: 30455735

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Project description:BackgroundPoly-γ-glutamic acid (γ-PGA) is a valuable polymer with glutamate as its sole precursor. Enhancement of the intracellular glutamate synthesis is a very important strategy for the improvement of γ-PGA production, especially for those glutamate-independent γ-PGA producing strains. Corynebacterium glutamicum has long been used for industrial glutamate production and it exhibits some unique features for glutamate synthesis; therefore introduction of these metabolic characters into the γ-PGA producing strain might lead to increased intracellular glutamate availability, and thus ultimate γ-PGA production.ResultsIn this study, the unique glutamate synthesis features from C. glutamicum was introduced into the glutamate-independent γ-PGA producing Bacillus amyloliquefaciens NK-1 strain. After introducing the energy-saving NADPH-dependent glutamate dehydrogenase (NADPH-GDH) pathway, the NK-1 (pHT315-gdh) strain showed slightly increase (by 9.1%) in γ-PGA production. Moreover, an optimized metabolic toggle switch for controlling the expression of ɑ-oxoglutarate dehydrogenase complex (ODHC) was introduced into the NK-1 strain, because it was previously shown that the ODHC in C. glutamicum was completely inhibited when glutamate was actively produced. The obtained NK-PO1 (pHT01-xylR) strain showed 66.2% higher γ-PGA production than the NK-1 strain. However, the further combination of these two strategies (introducing both NADPH-GDH pathway and the metabolic toggle switch) did not lead to further increase of γ-PGA production but rather the resultant γ-PGA production was even lower than that in the NK-1 strain.ConclusionsWe proposed new metabolic engineering strategies to improve the γ-PGA production in B. amyloliquefaciens. The NK-1 (pHT315-gdh) strain with the introduction of NADPH-GDH pathway showed 9.1% improvement in γ-PGA production. The NK-PO1 (pHT01-xylR) strain with the introduction of a metabolic toggle switch for controlling the expression of ODHC showed 66.2% higher γ-PGA production than the NK-1 strain. This work proposed a new strategy for improving the target product in microbial cell factories.

Dataset Information

Rewiring glycerol metabolism for enhanced production of poly-?-glutamic acid in Bacillus licheniformis.

Publications

Rewiring glycerol metabolism for enhanced production of poly-γ-glutamic acid in <i>Bacillus licheniformis</i>.

Similar Datasets

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