Production of Exopolysaccharides by Bacteria Isolated from River Water Using Banana and Yam Peels as Substrates

Abstract

The rising interest in microbial exopolysaccharides (EPS) has prompted the search for cost-effective substrates and efficient bacterial strains to enhance production. This study investigated river water as a source of EPS-producing bacteria and evaluated banana and yam peels as potential agro-residues for fermentation. River water samples (A, B, C) were enumerated for total heterotrophic bacterial counts, and isolates were characterized based on biochemical properties. Proximate analysis of banana and yam peels was carried out to determine their nutritional composition, while fermentation parameters including time, inoculum size, pH, carbon ratio concentration, and nitrogen concentration were optimized to maximize EPS yield. The results showed that heterotrophic bacterial counts ranged from 1.01 × 10⁵ to 1.08 × 10⁵ CFU/ml, with sample A recording the highest. Biochemical characterization revealed diverse bacterial genera including Staphylococcus, Bacillus, Pseudomonas, Klebsiella, Corynebacterium, Enterobacter, and Micrococcus species. Screening revealed isolate B2 (Bacillus sp.) as the best EPS producer, with a yield of 5.8 g/L, while the least production was observed in isolate A2 (0.3 g/L). Proximate analysis showed that banana peel contained higher ash (7.70%) and moisture (18.50%) contents, whereas yam peel exhibited higher lipid (7.75%) and protein (0.40%) contents. Both residues were carbohydrate-rich (67–68%), confirming their suitability as fermentation substrates. Optimization studies indicated that maximum EPS production was achieved at 72 h (9.1 g/L), 6% inoculum size (7.3 g/L), pH 6.0 (6.5 g/L), and a 2:2% banana peel:yam peel ratio (8.95 g/L). Supplementation with 0.4% yeast extract yielded a concentration of 6.3 g/L EPS. It is concluded that river water harbors diverse bacterial strains with significant EPS-producing potential and that banana and yam peels are viable low-cost substrates for sustainable EPS production under optimized fermentation conditions.