Simultaneous production of poly-γ-glutamic acid and 2,3-butanediol by a newly isolated Bacillus subtilis CS13

Abstract Background: Bacillus subtilis naturally produces large amounts of 2,3-butanediol (2,3-BD) as the main byproduct during poly-γ-glutamic acid (γ-PGA) fermentation using carbon sources. 2,3-BD is a promising platform chemicals in various industries, and co-production has great economic benefits. Thus, co-production of poly-γ-glutamic acid (γ-PGA) and 2,3-butanediol (2,3-BD) by Bacillus subtilis were investigated for the first time. Results: In this study, a novel Bacillus subtilis CS13 was isolated that can efficiently co-production of γ-PGA and 2,3-BD. The fermentation medium and culture parameters by B. subtilis CS13 were optimized using statistical methods. It was observed that sucrose, L-glutamic acid, ammonium citrate, and MgSO4·7H2O were favorable for γ-PGA and 2,3-BD co-production at pH 6.5 and 37 °C. A medium composed of 119.83 g/L sucrose, 48.85 g/L L-glutamic acid, 21.08 g/L ammonium citrate, and 3.21 g/L MgSO4·7H2O was optimized by response surface methodology (RSM). The results show that the yields of γ-PGA and 2,3-BD reached 27.79 ± 0.87 g/L at 24 h and 57.05 ± 1.28 g/L at 84 h with the optimized medium, respectively. Conclusions: To our knowledge, the co-production of 2,3-BD and γ-PGA will reduce the costs of production and separation in theory and provide a new perspective for industrial production of γ-PGA and 2,3-BD. B. subtilis CS13 as a generally recognized as safe (GRAS) strain, has great promise for the co-production of 2,3-BD and γ-PGA.