Xueping Guo

Improved poly-γ-glutamic acid production by chromosomal integration of the Vitreoscilla hemoglobin gene (vgb) in Bacillus subtilis

In order to alleviate oxygen limitation and improve the yield of poly-gamma-glutamic acid (gamma-PGA) during fermentation, the Vitreoscilla hemoglobin gene (vgb) was integrated into the chromosome of Bacillus subtilis and expressed during gamma-PGA production. The activity of the expressed Vitreoscilla hemoglobin (VHb) was confirmed by CO-difference spectrum. Expression of VHb enhanced cell growth under high viscosity fermentation conditions 1.26-fold and increased the yield of gamma-PGA 2.07-fold. These results indicate that the expression of VHb could be advantageous in high viscosity fermentation media.

Improvement of xylanase production by thermophilic fungus Thermomyces lanuginosus SDYKY-1 using response surface methodology.

Response surface methodology (RSM) was employed to optimize medium composition for the production of a thermostable xylanase from T. lanuginosus SDYKY-1 using economical carbon and nitrogen sources (soybean meal and corncobs, respectively). Plackett-Burman (P-B) design was applied to evaluate the effects of nine variables (powdered corncobs, soybean meal, Tween-80, CaCl(2), MgSO(4)·7H(2)O, FeSO(4), KH(2)PO(4), initial pH and inoculum culture volume). Corncobs, soybean meal and FeSO(4) were found to significantly influence on the xylanase production. The concentrations of these three factors were therefore optimized using central composite design and RSM. Adjusting the concentration of corncobs to 38.7g/L, soybean meal to 17.5g/L and FeSO(4) to 0.26g/L favored maximum xylanase production. Xylanase activity of 3078U/mL was obtained after optimization, which was a 144% increase that obtained before optimization (1264U/mL).