A novel approach for poly-γ-glutamic acid production using xylose and corncob fibres hydrolysate in Bacillus subtillis HB-1

BACKGROUND Poly-gamma-glutamic acid (gamma-PGA) is an extracellular anionic polymer with various potential applications. Renewable and economical carbon sources as the major fermentation feedstock are in need for gamma-PGA production. RESULTS Xylose has been demonstrated to support cell growth and gamma-PGA biosynthesis in Bacillus subtilis HB-1. Batch fermentation using xylose could produce about 23.63 g L-1 gamma-PGA in the broth with a high production rate of 0.74 g L-1 h(-1). Subsequent fed-batch fermentation could further improve the concentration of gamma-PGA up to 28.15 g L-1 with a high conversion rate of 0.97 g g(-1) (l-glutamate). Based on these preliminary results, the multiple-sugar containing substrate (corncob fibres hydrolysate) was chosen as the alternative complex carbon source to produce gamma-PGA, and one high concentration (24.92 g L-1) of gamma-PGA was attained. CONCLUSIONS Our pilot trial results suggested that the low-cost and renewable lignocellulosic biomass can be used for the environmental friendly and efficient production of gamma-PGA. (c) 2013 Society of Chemical Industry