Efficient production of poly-?-glutamic acid by Bacillus velezensis via solid-state fermentation and its application

A novel glutamate-dependent poly-gamma-glutamic acid (gamma-PGA)-producing strain Bacillus velezensis CAU263 isolated from Chinese traditional Douchi was evaluated. An efficient method of gamma-PGA production was performed by this strain via solid-state fermentation (SSF) using guar meal. The maximal yield of gamma-PGA reached 158.5 g/kg dry weight (DW) in 250 mL flasks and 155.1 g/kg DW in shallow tray, respectively. The molecular weight of gamma-PGA was 3.8 x 10(6) Da, the ratio of L/D-glutamic acid was 26.1% and 73.9%. Additionally, gamma-PGA significantly improved the operating characteristics of wheat dough, the specific volume of bread was increased by 15.8% and the bread hardness was reduced by 44.2% owing to the addition of 0.3 g/kg gamma-PGA. Thus, gamma-PGA could be produced by Bacillus velezensis CAU263 at high level using guar meal and might have potential application prospect in food industry.