Abstract: Streptococcus zooepidemicus NN-7 was subjected to mutagenesis by means of low energy ion implantation of 8×1014 N+/cm2 dose at 30 keV. After culture in selective medium, the mutant strains with double deficiency of hemolysin and hyaluronic acid-degrading enzyme were screened. Among these strains, a mutant strain capable of producing a high yield of hyaluronic acid was selected and designated as SH-9. The strain still revealed excellent passage stability after six generations. The yield of hyaluronic acid reached up to 3.23 g/L with determined relative molecular weight (Mr) of 2.12×106. Compared with the original parent strain, the yield and molecular weight of hyaluronic acid derived from SH-9 were increased by 104.4%and 35.9%, respectively.

Key words: hyaluronic acid, Streptococcus zooepidemicus, ion implantation, mutation screening