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-γ-glutamic acid (γ-PGA) during fermentation, the Vitreoscilla hemoglobin gene (vgb) was integrated into the chromosome of Bacillus subtilis and expressed during γ-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 γ-PGA 2.07-fold. These results indicate that the expression of VHb could be advantageous in high viscosity fermentation media.