Agro-industrial Residues: Low-cost Biomass for the Production of Bioactive Extracellular Polysaccharides by Lactobacillus plantarum in Solid State Fermentation

Abstract

Agro-residues, such as apple peel, banana peel, orange peel, tapioca peel, and sweet potato peel powders, were screened for the biosynthesis of bioactive extracellular polysaccharide (EPS) in solid-state fermentation. Lactobacillus plantarum utilized sweet potato peel and improved EPS production compared with other wastes, so it was used for optimization studies. Compared with the unoptimized medium, the response surface methodology improved EPS production twofold during solid-state fermentation. In the central composite design, the experimental model was significant (p<0.01), and the selected variables (moisture, sucrose and yeast extract) significantly influenced EPS production. The maximum yield was 59.1 mg/g with 64.5% moisture content, 5.74% sucrose, and 1.39% yeast extract. In addition, the extracted EPS exhibited strong antioxidant activity, and it scavenged ABTS, DPPH, and hydroxyl radicals in a concentration-dependent manner. The antibacterial activity of EPS was greatest against Staphylococcus aureus, and the corresponding zone of inhibition was18±1 mm, followed by Pseudomonas aeruginosa(14±1 mm).The results showed that sweet potato peels can be used as a cheap substrate for EPS production in solid-state fermentation.