Valorization of Riceberry Broken Rice and Soybean Meal for Optimized Production of Multifunctional Exopolysaccharide by PS21 with Potent Bioactivities Using Response Surface Methodology.

This study explores the valorization of agro-industrial by-products-riceberry broken rice (RBR) and soybean meal (SBM)-as cost-effective substrates for enhancing exopolysaccharide (EPS) production by PS21. Eight strains were screened, and PS21 demonstrated the highest EPS yield (2.54 g/100 mL DW). The EPS displayed a strong antioxidant capacity with 65.5% DPPH and 80.5% hydroxyl radical scavenging, and a FRAP value of 6.51 mg Fe/g DW. Antimicrobial testing showed inhibition zones up to 10.07 mm against and 7.83 mm against . Optimization using central composite design (CCD) and the response surface methodology (RSM) revealed the best production at 5% (/) RBR, 3% (/) SBM, pH 6.66, and 39.51 °C, yielding 39.82 g/L EPS. This EPS is a moderate-molecular-weight (11,282 Da) homopolysaccharide with glucose monomers. X-ray diffraction (XRD) showed an amorphous pattern, favorable for solubility in biological applications. Thermogravimetric analysis (TGA) demonstrated thermal stability up to ~250 °C, supporting its suitability for high-temperature processing. EPS also exhibited anticancer activity with IC values of 226.60 µg/mL (MCF-7) and 224.30 µg/mL (HeLa) at 72 h, reduced colony formation, inhibited cell migration, and demonstrated anti-tyrosinase, anti-collagenase, and anti-elastase effects. This study demonstrates the successful valorization of agro-industrial by-products-RBR and SBM-for the high-yield production of multifunctional EPS with potent antioxidant, antimicrobial, and anticancer properties. The findings highlight the sustainable potential of these low-cost substrates in supporting the development of green and value-added bioproducts, with promising utilizations across the food, pharmaceutical, and cosmetic sectors.