Metabolic studies of temperature control strategy on poly(γ-glutamic acid) production in a thermophilic strain Bacillus subtilis GXA-28

A thermophilic strain Bacillus subtilis GXA-28 with capability of gamma-PGA production was characterized, and its product was identified. The effect of temperatures on cell growth, gamma-PGA yield and molecular weight were investigated. Results showed that gamma-PGA yield reached 19.92 g/L at 45 degrees C with a high productivity of 0.91 g/L/h, and the molecular weight reached 3.03 x 10(6) Da. Then, the flux distribution and the key enzyme activities at 2-oxoglutarate branch under specified temperature were determined to illustrate the possible metabolic mechanism contributing to the improved gamma-PGA production. Results indicated that the fluxes from iso-citrate to 2-oxoglutarate and from 2-oxoglutarate to glutamate were increased with high activity of isocitrate dehydrogenase and glutamate dehydrogenase, which led to enhance gamma-PGA production. This work firstly employed temperature control strategy to improve gamma-PGA production, and provided novel information on the metabolic mechanism of gamma-PGA biosynthesis in Bacillus species. (C) 2013 Elsevier Ltd. All rights reserved.