초록
Hyaluronic acid (HA) production in Streptococcus zooepidemicus competes for the carbon source along with biomass formation, lactate formation (via glycolysis) and pentose phosphate pathway (PPP). In our studies, increase in HA molecular weight was observed by redirecting the carbon flux towards HA biosynthesis pathway by partially inhibiting the glycolytic pathway. Batch bioreactor (1.2L) studies showed that with the addition of 25μM sodium iodoacetate, 5g/L tryptophan and 10g/L pyruvate, which are glycolytic inhibitors, HA molecular weight increased to 3.2, 3.2 and 3.1MDa respectively compared to control run (2.4MDa). Yield coefficients Y<SUB>HA/S</SUB> and Y<SUB>LA/S</SUB> showed inverse relationship, indicating competition for glucose between HA and lactic acid formation. Addition of 5g/L glutamine along with 25μM sodium iodoacetate also increased the HA concentration to 5.0g/L from 2.0g/L in control run. Metabolic flux analysis studies show that concentration and molecular weight of HA is increased by decreasing carbon flux towards glycolysis and PPP and increasing carbon flux towards HA precursor formation. It was observed that specific growth rate of the cells correlated positively to the specific HA production rate and negatively to the molecular weight of HA produced. Addition of antioxidant tannic acid also increased molecular weight to 3.0MDa.