Sha Y, Zhang Y, Qiu Y, Xu Z, Li S, Feng X, Wang M, Xu H. Efficient Biosynthesis of Low-Molecular-Weight Poly-γ-glutamic Acid by Stable Overexpression of
PgdS Hydrolase in Bacillus amyloliquefaciens NB.
J Agric Food Chem 2019;
67:282-290. [PMID:
30543111 DOI:
10.1021/acs.jafc.8b05485]
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Abstract
Low-molecular-weight poly-γ-glutamic acid (LMW-γ-PGA) has attracted much attention owing to its great potential in food, agriculture, medicine, and cosmetics. Current methods of LMW-γ-PGA production, including enzymatic hydrolysis, are associated with low operational stability. Here, an efficient method for stable biosynthesis of LMW-γ-PGA was conceived by overexpression of γ-PGA hydrolase in Bacillus amyloliquefaciens NB. To establish stable expression of γ-PGA hydrolase (PgdS) during fermentation, a novel plasmid pNX01 was constructed with a native replicon from endogenous plasmid p2Sip, showing a loss rate of 4% after 100 consecutive passages. Subsequently, this plasmid was applied in a screen of high activity PgdS hydrolase, leading to substantial improvements to γ-PGA titer with concomitant decrease in the molecular weight. Finally, a satisfactory yield of 17.62 ± 0.38 g/L LMW-γ-PGA with a weight-average molecular weight of 20-30 kDa was achieved by direct fermentation of Jerusalem artichoke tuber extract. Our study presents a potential method for commercial production of LMW-γ-PGA.
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