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Mutations in genes encoding antibiotic substances increase the synthesis of poly-?-glutamic acid in Bacillus amyloliquefaciens LL3.

ABSTRACT: Poly-?-glutamic acid (?-PGA) is an important natural biopolymer that is used widely in fields of foods, medicine, cosmetics, and agriculture. Several B. amyloliquefaciens LL3 mutants were constructed to improve ?-PGA synthesis via single or multiple marker-less in-frame deletions of four gene clusters (itu, bae, srf, and fen) encoding antibiotic substances. ?-PGA synthesis by the ?srf mutant showed a slight increase (4.1 g/L) compared with that of the wild-type strain (3.3 g/L). The ?itu?srf mutant showed increased ?-PGA yield from 3.3 to 4.5 g/L, with an increase of 36.4%. The ?-PGA yield of the ?itu?srf?fen and ?itu?srf?fen?bae mutants did not show a further increase. The four gene clusters' roles in swarming motility and biofilm formation were also studied. The ?srf and ?bae mutant strains were both significantly defective in swarming, indicating that bacillaene and surfactin are involved in swarming motility of B. amyloliquefaciens LL3. Furthermore, ?srf and ?itu mutant strains were obviously defective in biofilm formation; therefore, iturin and surfactin must play important roles in biofilm formation in B. amyloliquefaciens LL3.

SUBMITTER: Gao W

PROVIDER: S-EPMC5300885 | biostudies-other | 2017 Feb

REPOSITORIES: biostudies-other

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Mutations in genes encoding antibiotic substances increase the synthesis of poly-γ-glutamic acid in Bacillus amyloliquefaciens LL3.

Gao Weixia W Liu Fenghong F Zhang Wei W Quan Yufen Y Dang Yulei Y Feng Jun J Gu Yanyan Y Wang Shufang S Song Cunjiang C Yang Chao C

MicrobiologyOpen 20160818 1

Poly-γ-glutamic acid (γ-PGA) is an important natural biopolymer that is used widely in fields of foods, medicine, cosmetics, and agriculture. Several B. amyloliquefaciens LL3 mutants were constructed to improve γ-PGA synthesis via single or multiple marker-less in-frame deletions of four gene clusters (itu, bae, srf, and fen) encoding antibiotic substances. γ-PGA synthesis by the Δsrf mutant showed a slight increase (4.1 g/L) compared with that of the wild-type strain (3.3 g/L). The ΔituΔsrf mut ...[more]

PMID: 27539744

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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

Mutations in genes encoding antibiotic substances increase the synthesis of poly-?-glutamic acid in Bacillus amyloliquefaciens LL3.

Publications

Mutations in genes encoding antibiotic substances increase the synthesis of poly-γ-glutamic acid in Bacillus amyloliquefaciens LL3.

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