The Welan Gum producing strain was selected from the laboratory preservation strain as parent strain of breeding,many mutants were obtained by the Welan Gum producting strain with UV irradiation.The Welan Gum producing strain NC-2 was selected by plate, shake flask culture and generation experiments.Then the optimum fermentation medium was ensured by orthogonal design. It was showed that the prime fermentation medium contain.sucrose 40g/L, yeast extract 3g/L, K2HPO4 · 7H2O 5g/L, MgSO4·7H2O 4g/L, FeSO4·7H2O 1mg/L, CaCl2 0.5g/L,the yield of...