Abstract: Xanthomonas campestris XG30-18 was radiated by microwave and then treated with nitrosoguanidine (NTG) and a mutant strain named as MW-42-NTG-6 was obtained. The strain had the ability to produce high-viscosity and acid-resistant xanthan gum. The optimal carbon and nitrogen sources for the strain were sucrose + corn starch and soybean protein isolate, respectively. The optimal fermentation conditions for production of high-viscosity and acid-resistant xanthan gum by the strain, as determined using orthogonal array design method, were inoculum amount of 8%, fermentation pH of 7.0, rotation speed of 240 r/min and fermentation temperature of 28 ℃. Under these conditions, the viscosity, yield, acid-resistant pH of xanthan gum were 1790 cP, 3.92% and 4.2, respectively.

Key words: Xanthomonas campestris, xanthan gum, NTG mutation, microwave mutation, acid resistance, fermentation