Optimization of hyaluronic acid production through co-culture of mutant Streptococcus zooepidemicus and Streptococcus pyogenes under controlled uv and environmental conditions.

This study aimed to investigate the effects of UV radiation intensity, exposure time, and distance on HA production in phenotypically selected UV-derived strains of Streptococcus zooepidemicus and Streptococcus pyogenes, and to determine the optimal environmental and co-culture conditions for maximum HA yield. Wild-type strains of S. zooepidemicus and S. pyogenes were exposed to varying UV intensities (8 W and 30 W), exposure times, and distances, followed by phenotypic screening of resulting isolates. Following sequential phenotypic screening and quantitative HA evaluation, the highest-producing UV-derived isolates were selected for subsequent fermentation optimization. Fermentations were then carried out at different temperatures and pH values to determine the optimal conditions for growth and HA synthesis. Additionally, competitive fermentations were conducted using co-cultures of phenotypically selected UV-derived S. zooepidemicus (MSz) and S. pyogenes (MSp) at varying inoculation ratios. Optimal HA production for S. zooepidemicus was observed at 37 °C and pH 7, with maximum yield achieved under 30 W UV radiation from a 30 cm distance for 12 s. S. pyogenes exhibited the highest HA production at 35 °C and pH 8 under 30 W UV applied from 25 cm for 8 s. Co-culturing MSz and MSp at a 1:1 inoculation ratio significantly enhanced HA yield compared to monocultures, suggesting a potential beneficial interaction associated with enhanced HA biosynthesis. The overall maximum HA concentration was 1421.38 mg/L, obtained from the 1:1 co-culture of MSz and MSp at 37 °C and pH 6.5, corresponding to an average volumetric productivity of 0.237 g/L/h over the 6-h fermentation period. Temperature, pH, and UV exposure parameters play a pivotal role in optimizing HA production. Moreover, the co-culture of MSz and MSp presents a promising strategy for further development of HA production processes, offering higher productivity than monoculture fermentations.