Development of Jerusalem artichoke resource for efficient one-step fermentation of poly-(γ-glutamic acid) using a novel strain Bacillus amyloliquefaciens NX-2S

This study aimed to develop non-food fermentation for the cost-effective production of poly-(gamma-glutamic acid) (gamma-PGA) using a novel strain of Bacillus amyloliquefaciens NX-2S. The new isolate assimilated inulin more efficiently than other carbohydrates from Jerusalem artichoke, without hydrolytic treatment. To investigate the effect of inulin on gamma-PGA production, the transcript levels of gamma-PGA synthetase genes (pgsB, pgsC, pgsA), regulatory genes (comA, degQ, degS), and the glutamic acid biosynthesis gene (glnA) were analyzed; inulin addition upregulated these key genes. Without exogenous glutamate, strain NX2S could produce 6.85 +/- 0.22 g/L of gamma-PGA during fermentation. Exogenous glutamate greatly enhances the gamma-PGA yield (39.4 +/- 0.38 g/L) and productivity (0.43 +/- 0.05 g/L/h) in batch fermentation. Our study revealed a potential method of non-food fermentation to produce high-value products. (C) 2017 Published by Elsevier Ltd.