Optimization Feed Composition on Hyaluronic Acid Production of in-Batch and Fed-Batch Cultures of Streptococcus zooepidemicus

Hyaluronic acid (HA), as a high-value-added biological product, is one of the most widely used biopolymers in industry and medicine. This study aimed to increase HA production by carefully investigating the effect of glucose concentration, type and concentration of nitrogen source in batch culture, and control of glucose concentration in fed-Batch culture on HA production. The effect of two different nitrogen sources of hydrolyzed casein and tryptone soy broth on HA production was investigated in batch cultures of Streptococcus zooepidemicus. Then, the effect of glucose concentration on HA production was studied in batch and fed-batch cultures. Under optimal conditions, including hydrolyzed casein 20 g/L and an initial glucose concentration of 30 g/L in batch culture, 4.4 g/L HA was obtained. Also, constant feeding of 30 g/L of glucose increased HA production to 5.8 g/L. This amount is one of the highest HA production values ever reported in fed-batch cultures at a constant feeding rate. Weakening of the glycolytic cycle and slowing down the cell growth rate affect the increase of HA production. Also, controlling the concentration of glucose as a source of energy and carbon in the cells by the fed-batch culture can be directed the cell pathway to more hyaluronic acid production and higher yield.