Multifunctional bioactivity of marine-derived exopolysaccharide EPSR5 from Kocuria sp. AG5: insights into structural and broad-spectrum biomedical applications

Abstract

Marine bacteria are a valuable source of bioactive polysaccharides with therapeutic potential. In our previous study, we identified an exopolysaccharide produced by Kocuria sp. strain AG5 (EPSR5) isolated from the Red Sea, and demonstrated that it is a high-molecular weight, acidic heteropolysaccharide rich in sulfate (25.6%) and uronic acid (21.77%) groups. In the current study, we expanded the structural characterization and biological evaluation of EPSR5. GC–MS and HPLC analyses revealed glucose as the major monosaccharide, accompanied by xylose, arabinose, and glucuronic acid, confirming its heteropolysaccharide and polyanionic character. Thermal analysis (TGA) demonstrated stability up to 257 °C, while SEM–EDX revealed a porous, flake-like morphology enriched in oxygen, sodium, and phosphorus, suggesting phosphorylation and ionic associations. The biological activity of EPSR5 was assessed through a range of pharmacological assays. Antimicrobial testing against seven pathogenic microbes, including two fungal strains (Candida albicans, Mucor circinelloides), two Gram-positive bacteria (Enterococcus faecalis, Staphylococcus aureus), and three Gram-negative bacteria (Escherichia coli, Salmonella typhi, Helicobacter pylori), demonstrated potent inhibitory effects. EPSR5 showed notable inhibition zones up to 30 mm against E. faecalis and 27 mm against H. pylori, with MIC/MBC values as low as 7.8/15.62 μg mL⁻¹ and 15.62/15.62 μg mL⁻¹, respectively. Significant antibiofilm activity was also observed, with inhibition rates reaching up to 96.54% against E. faecalis and 97.39% against H. pylori, in a concentration-dependent manner. Antioxidant potential was confirmed via TAC and FRAP assays, showing values of 62.8 ± 0.3 and 114.9 ± 0.5 μg ascorbic acid equivalents per mg, respectively. EPSR5 exhibited antidiabetic activity by inhibiting α-glucosidase and α-amylase enzymes with IC₅₀ values of 17.06 μg mL⁻¹ and 66.35 μg mL⁻¹, respectively, comparable to Acarbose. Additionally, EPSR5 inhibited pancreatic lipase with an IC₅₀ of 41.39 μg mL⁻¹ and suppressed 90.1% of enzyme activity at 1000 μg mL⁻¹. In wound healing assays, EPSR5 promoted fibroblast migration and accelerated wound closure, reducing the wound area within 48 hours, achieving 71.85% closure compared to 66.24% in control cells. Overall, these findings suggest that EPSR5 from Kocuria sp. AG5 exhibits multifaceted bioactivities with promising therapeutic potential for antimicrobial, antioxidant, antidiabetic, and wound healing applications.