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

• Published in: Applied microbiology and biotechnology 2020-08, Vol.104 (16)
• Main Authors: Wang, Dexin, Kim, Hyangmi, Lee, Sungbeom, Kim, Dae-Hyuk, Joe, Min-Ho
• Format: Article
• Language: English
• Subjects: Amino acids; Butanediol; Fermentation; Glutamate; Nuclear energy
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-020-10755-0

Bacillus subtilis naturally produces large amounts of 2,3-butanediol (2,3-BD) as a main by-product during poly-[gamma]-glutamic acid ([gamma]-PGA) production. 2,3-BD is a promising platform chemical in various industries, and co-production of the two chemicals has great economic benefits. Co-production of [gamma]-PGA and 2,3-BD by a newly isolated B. subtilis CS13 was investigated here. The fermentation medium and culture parameters of the process were optimized using statistical methods. It was observed that sucrose, l-glutamic acid, ammonium citrate, and MgSO.sub.4·7H.sub.2O were favorable for [gamma]-PGA and 2,3-BD co-production at culture pH of 6.5 and 37 °C. An optimal medium composed of 119.8 g/L sucrose, 48.8 g/L l-glutamic acid, 21.1 g/L ammonium citrate, and 3.2 g/L MgSO.sub.4·7H.sub.2O was obtained by response surface methodology (RSM). The results show that the titers of [gamma]-PGA and 2,3-BD reached 27.8 ± 0.9 g/L at 24 h and 57.1 ± 1.3 g/L at 84 h with the optimized medium, respectively. [gamma]-PGA and 2,3-BD production by B. subtilis CS13 was significantly enhanced in fed-batch fermentations. [gamma]-PGA (36.5 ± 1.1 g/L, productivity of 1.22 ± 0.04 g/L/h) and 2,3-BD concentrations (119.6 ± 2.8 g/L, productivity of 2.49 ± 0.66 g/L/h) were obtained in the optimized medium with feeding sucrose. The co-production of 2,3-BD and [gamma]-PGA provides a new perspective for industrial production of [gamma]-PGA and 2,3-BD.Key points