Engineering of recombinant Escherichia coli cells co-expressing poly-?-glutamic acid (?-PGA) synthetase and glutamate racemase for differential yielding of ?-PGA.
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ABSTRACT: Poly-?-glutamic acid (?-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 ?-PGA synthetase genes pgsBCA and glutamate racemase gene racE from both L-glutamate-dependent ?-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 ?-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 ?-PGA production. Furthermore, RacE integration could enhance ?-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 ?-PGA.
SUBMITTER: Cao M
PROVIDER: S-EPMC3815934 | biostudies-literature | 2013 Nov
REPOSITORIES: biostudies-literature
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