Influence of competing metabolic processes on the molecular weight of hyaluronic acid synthesized by Streptococcus zooepidemicus

Hyaluronic acid (HA) is a linear high molecular weight glycosaminoglycan polymer with its molecular weight determining its physiological role, rheological properties and applications. The commercially used microbial source—Streptococcus zooepidemicus is incapable of synthesizing very high molecular weight polymer with low polydispersity, an essential niche in the HA market. In this organism, three important metabolic processes—glycolysis, hyaluronic acid synthesis and biomass formation compete for carbon source, nitrogen source, energy and precursors to determine the molecular weight of the synthesized polymer. After studying the role of culture conditions on these competing processes, it was found that the best strategy for enhancing molecular weight was to weaken the glycolytic process, strengthen HA synthesis process and maintain nitrogen under limiting condition to reduce the rate of biomass formation. Based on this newly developed strategy—temperature switches, addition of precursor N-acetylglucosamine and addition of pyruvate experiments enhanced the molecular weight of the polymer by 23%, 74% and 64%, respectively. Improving precursor levels, particularly UDP-N-acetylglucosamine and thereby strengthening the HA flux plays a direct role in improving molecular weight of hyaluronic acid.