Abstract: wild streptococcus zooepidemicus 　C55151 was mutated by N-methyl-N-nitro-N-nitrosogua-nidin(NTG), a mutanted strain(J18) capable of producing HA in a high yield was acquired, which can produce HA twice as much as the original strain. The optimum fer mentation culture medium was studied by an orthogonal method, which contained glucose 50 g/L, yeast extract paste 30 g/L,MgSO₄ 0.5 g/L. It was found that SDS can improve the yield of HAobviously. The kinetics of the HA fermentation process of the original one was compared with that of the mutanted strain.

Key words: streptococcus zooepidemicus, hyaluronic acid, mutation, fermentation