Effect of Environmental Factors on Production of Hyaluronic Acid by Streptococcus zooepidemicus

The effects of various environmental factors on the production of hyaluronic acid (HA) by Streptococcus zooepidemicus BCRC15414, the quantitation of HA by HPLC and morphology of the strain were examined. The cell growth was enhanced by aeration and agitation, but the influence of aeration was significantly higher. Agitation enhanced the HA production, but aeration has no beneficial effect for the HA production. Aeration and agitation significantly increased the kLa values; however, the kLa is not a determined factor for the HA production. A two-stage anoxic (static)-aerobic sequential culture, which is static for 24 h followed by aeration at 2 L/min, led to superior results both in biomass and HA production at the end of cultivation. The optimal initial glucose concentrations was about 20g/L, which led to highest HA production (0.51 g/L) after 24 h of cultivation in the two-stage anoxic (static)-aerobic sequential culture. The average molecular weight (Mw) of HA produced was 3.0×103 kDa, which was not affected by the glucose concentration used. Meanwhile, the addition of nisin enhanced the glucose consumption, biomass and HA production. Substrate inhibition on HA production was observed for S. zooepidemicus BCRC15414 when the initial glucose concentration was above the optimal value ( > 20 g/L); no substrate inhibition on cell growth was observed. In the quantitation of HA, HA concentration analyzed by HPLC method was more accurate than that analyzed by carbazole method. Distinctive differences of morphologies were observed for the low and high HA producing strains, which provides a simple and important tool that enable one to screen and identify the ability of a strain to produce high titer of HA.