Influence of initial glucose and lactic acid concentration on hyaluronic acid production by Streptococcus zooepidemicus: Kinetic and modeling

Abstract

Hyaluronic acid (HA) is a molecule of significant commercial value with applications in the pharmaceutical, cosmetic, and medical industries. It is typically produced through microbial fermentation. However, the efficiency of this type of process can be affected by inhibition phenomena due to the substrate or the product. In this sense, the effect of different initial concentrations of glucose (9.3–59.9 g/L) and lactic acid (10.7–56.0 g/L) was studied in the present investigation to determine their effect on the growth of Streptococcus zooepidemicus and HA production in batch fermentation. The maximum HA concentration obtained was 3.3 g/L from 59.9 g/L glucose, while productivity, yield, and specific rate of HA formation were higher at 31.9 g/L glucose. The biomass produced followed a stepwise pattern with increasing glucose, although the specific growth rate decreased after reaching 39.1 g/L glucose. The initial presence of lactic acid (LA) hurt fermentation, decreasing the amount of biomass and HA produced; the inhibitory effect of LA was more pronounced at 19.4 g/L and above, decreasing productivities, yields, and specific rates. Compared to experimental data, the proposed mathematical model described satisfactorily (R2 > 0.9) the dynamics of the fermentation process at different culture conditions.