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Metab Eng. 2019 Jul 22;55:239-248. doi: 10.1016/j.ymben.2019.07.009. [Epub ahead of print]

Tailor-made poly-γ-glutamic acid production.

Author information

1
Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany.
2
Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, 565-0871, Osaka, Japan.
3
Institute of Applied Microbiology-iAMB, Aachen Biology and Biotechnology-ABBt, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany. Electronic address: lars.blank@rwth-aachen.de.

Abstract

Poly-γ-glutamic acid (γ-PGA), which is produced by several Bacillus species, is a chiral biopolymer composed of D- and L-glutamate monomers and has various industrial applications. However, synthesized γ-PGA exhibits great structural diversity, and the structure must be controlled to broaden its industrial use. The biochemical pathways for γ-PGA production suggest that the polymer properties molecular weight (MW) and stereochemical composition are influenced by (1) the affinity of γ-PGA synthetase for the two alternative glutamate enantiomers and (2) glutamate racemase activity; hence, the availability of the monomers. In this study, we report tailor-made γ-PGA synthesis with B. subtilis by combining PGA synthetase and glutamate racemase genes from several Bacillus strains. The production of structurally diverse γ-PGA was thereby achieved. Depending on the PGA synthetase and glutamate racemase origins, the synthesized γ-PGA contained 3-60% D-glutamate. The exchange of PGA synthetase changed the MW from 40 to 8500 kDa. The results demonstrate the production of low-, medium-, and high-MW γ-PGA with the same microbial chassis.

KEYWORDS:

Bacillus; Biopolymer; Chassis; Metabolic engineering; Polyglutamate; γ-PGA

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