Bacillus subtilisnaturally 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 isolatedB. subtilisCS13 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 MgSO4 center dot 7H(2)O were favorable for gamma-PGA and 2,3-BD co-production at culture pH of 6.5 and 37 degrees C. An optimal medium composed of 119.8 g/L sucrose, 48.8 g/Ll-glutamic acid, 21.1 g/L ammonium citrate, and 3.2 g/L MgSO4 center dot 7H(2)O 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 byB. subtilisCS13 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.