title: Engineering of recombinant Escherichia coli cells co-expressing poly-γ-glutamic acid (γ-PGA) synthetase and glutamate racemase for differential yielding of γ-PGA.
abstract: Poly-γ-glutamic acid (γ-PGA) is a promising environmental-friendly material with outstanding water solubility, biocompatibility and degradability. However, it is tough to determine the relationship between functional synthetic enzyme and the strains' yield or substrate dependency. We cloned γ-PGA synthetase genes pgsBCA and glutamate racemase gene racE from both L-glutamate-dependent γ-PGA-producing Bacillus licheniformis NK-03 and L-glutamate-independent B. amyloliquefaciens LL3 strains. The deduced RacE and PgsA from the two strains shared the identity of 84.5% and 78.53%, while PgsB and PgsC possessed greater similarity with 93.13% and 93.96%. The induced co-expression of pgsBCA and racE showed that the engineered Escherichia coli strains had the capacity of synthesizing γ-PGA, and LL3 derived PgsBCA had higher catalytic activity and enhanced productivity than NK-03 in Luria-Bertani medium containing glucose or L-glutamate. However, the differential effect was weakened when providing sufficient immediateness L-glutamate substrate, that is, the supply of substrate could be served as the ascendance upon γ-PGA production. Furthermore, RacE integration could enhance γ-PGA yield through improving the preferred d-glutamate content. This is the first report about co-expression of pgsBCA and racE from the two Bacillus strains, which will be of great value for the determination of the biosynthetic mechanism of γ-PGA.
authors.affiliation: Key Laboratory of Molecular Microbiology and Technology for Ministry of Education, Nankai University, Tianjin, 300071, China; Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, China.
authors.forename: Mingfeng
authors.initials: M
authors.lastname: Cao
authors.forename: Weitao
authors.initials: W
authors.lastname: Geng
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Jibin
authors.initials: J
authors.lastname: Sun
authors.forename: Shufang
authors.initials: S
authors.lastname: Wang
authors.forename: Jun
authors.initials: J
authors.lastname: Feng
authors.forename: Ping
authors.initials: P
authors.lastname: Zheng
authors.forename: Anna
authors.initials: A
authors.lastname: Jiang
authors.forename: Cunjiang
authors.initials: C
authors.lastname: Song
mesh_terms: D000591:Amino Acid Isomerases / Q000235:genetics* / Q000378:metabolism; D001407:Bacillus / Q000201:enzymology / Q000235:genetics; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D060847:Metabolic Engineering; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000235:genetics* / Q000378:metabolism; D011099:Polyglutamic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis
chemical_list: D001426:Bacterial Proteins; C511775:poly(gamma-glutamic acid); D011099:Polyglutamic Acid; D000591:Amino Acid Isomerases; C062292:glutamate racemase; D010453:Peptide Synthases; C022414:polyglutamyl synthetase
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