Nano-bio synergistic fermentation for nutrient valorization of agro-residues and environmental sustainability

Nano-bio synergistic fermentation (NBSF) was developed to enhance nutrient valorization of agro-residues by integrating zinc oxide (ZnO) nanoparticles with Aspergillus oryzae. Agricultural residues such as rice husk and sugarcane bagasse contain high amounts of structural carbohydrates but are limited by lignocellulosic recalcitrance. In this study, ZnO nanoparticles were characterized using TEM, DLS, zeta potential, XRD, FTIR, BET, UV-Vis, and EDX analyses and subsequently incorporated into solid-state fermentation. Fermentation performance was evaluated based on total soluble nutrients (TSN), protein enrichment, lignocellulosic degradation, and reductions in chemical oxygen demand (COD) and organic load. NBSF increased TSN to 95.3 ± 3.4 mg/g and protein content to 14.6 ± 1.1%, compared with microbial fermentation alone (58.3 ± 2.1 mg/g and 10.7 ± 0.8%, respectively). Cellulose, hemicellulose, and lignin contents decreased by 38.5, 44.2, and 23.1%, respectively. COD and organic load were reduced by 48 and 61%, demonstrating improved environmental performance. Statistical analysis using one-way ANOVA followed by Tukey's HSD confirmed significant differences among treatments (p < 0.001). The results indicate that combining ZnO nanoparticles with microbial fermentation enhances enzymatic hydrolysis, promotes nutrient recovery, and reduces environmental impact, offering a scalable strategy for sustainable agro-residue valorization.