Enhancement of superoxide dismutase activity using mixed Lactobacillus casei and Saccharomyces cerevisiae cultures in simulated gastrointestinal conditions with encapsulation

Superoxide dismutase (SOD)-producing microorganisms have attracted increasing attention given their scavenge superoxide anions capabilities, but further strengthening methods are still urgently needed. Herein, Lactobacillus casei F18 and Saccharomyces cerevisiae J14 were isolated for their high SOD activity. Co-culturing these two strains emerged effective nutritional cooperation, which increased SOD activity by 198.22% and 66.35% compared to F18 and J14, respectively. SOD activity of co-culture “F18 +J14” was further enhanced by response surface methodology and metal ion stress. High-performance liquid chromatographic and RT-qPCR analyses of “F18 +J14” revealed that SOD production pathways were active and contents of metabolites acetate and ethanol were dramatically increased. Metabolite complementarity experiment also verified the addition of acetate and ethanol in vitro enhanced SOD activity and gene expression of “F18 +J14”. These findings highlighted co-culture and metal ion stress enhanced SOD activity by cross-stimulating cells with metabolites, affecting cell growth, and up-regulating SOD genes. Furthermore, “F18 +J14” based immobilized bio-beads were successfully synthesized with sodium alginate combined CaCO3, which exhibited the highest cell vitality and SOD activity in the simulated gastrointestinal conditions. Together, this study revealed the synergistic promotion mechanism of SOD biosynthesis by co-cultivation lactic acid bacteria and yeast, and shows great promise for management of oxidation stress related diseases.