Optimization Of Xanthan Gum Fermentation Process And Strain Screening

Xanthan gum production was studied in this paper by Xanthomonas campestris pv.campestris 8004(Xcc 8004).The original xanthan gum production was only 1.21%.The main composition and concentration of the fermentation medium were determined by the single factor experiments.Then Box-Behnken Design(BBD)response surface analysis was used for the optimization of xanthan gum fermentation medium.The xanthan gum production was up to 2.18%at the concentration of sucrose 4.66%,soybean meal 0.5%and calcium carbonate 0.33%,improved by 80.16%than before.The optimum fermentation conditions were determined by single factor experiments.The xanthan gum production was up to 2.28%at the condition of seed age 15 h,4%inoculum concentration,initial pH of 7.5,cultivation temperature of 30?,rotation speed of 220rpm.The separation of xanthan gum was preliminary investigated by the method of orthogonal.The best separation process was as follows:fermentation broth was diluted to 5 times,1.2 times volume of ethanol was added to precipitate xanthan gum,pH was adjusted to 6.0,3mL of saturated KC1 was added for precipitation.The reco'very ratio was increased by 25.11%.The separated xanthan gum was detected according to national standard.The test results were as follows:1%sample was not dissolved in ethanol,acetone and ether,and completely dissolved in water,condensate was appeared in 1%sample solution after adding locust bean gum,the viscosity of 1%xanthan gum solution was 1050cp,the shear properties was 7.23,loss on drying was 10.57%,ash content was 14.67%,total nitrogen content was 0.63%,pyruvic acid content was up to grade.All this properties indicated that the xanthan gum product had reached standards of food grade xanthan gum.The impact of vitamin C(Vc)on xanthan gum production was investigated by addding Vc to the fermentation process.Though adding 20 mg·L-1 of Vc at 24 h in the fermentation broth,the xanthan gum production was improved by 9.38%.The concentration of living cells were greater than the control,so did the sucrose utilization and conversion rates.Meanwhile,Xcc 8004was mutagenized by ultraviolet(UV)and nitrous acid.UV-18 was screened by protoplast UV mutagenesis,xanthan gum production was reached to 2.29%,increased by 11.31%than that of Xcc 8004.Y-11 was screened by nitrous acid mutagenesis,and its xanthan gum production was up to 2.38%,enhanced by 12.58%compared with Xcc 8004.