Optimization of biomass production, morphology, architecture, and nutrient removal by Rhizopus oryzae M10A1 cultivated on potato starch processing effluents as a fungal cell factory

Background: The valorization of agro-industrial effluents through filamentous fungi represents a strategic pillar of the circular bioeconomy. Liquid residues generated during potato starch processing contain substantial carbon and nitrogen sources, making them suitable substrates for fungal biomass production. Despite this potential, few studies integrate statistical optimization, morphological characterization, and nutrient assimilation efficiency in a single bioprocess using defined Rhizopus oryzae strains. This study evaluates and optimizes biomass production, growth morphology, and nutrient removal efficiency of Rhizopus oryzae M10A1 cultivated in potato starch processing effluents under submerged fermentation. Results: Biomass production reached 15.70 g/L after optimization using response surface methodology at 35°C, pH 4, and 150 rpm, corresponding to approximately a 15% increase relative to the initial conditions. The quadratic model showed strong predictive performance (adjusted R² = 89.67%), adequate precision (18.19), and a non-significant lack of fit (p = 0.089). Nutrient removal efficiencies were 85.85% for total sugars, 80.49% for total starch, 74.29% for total nitrogen, and 70.90% for reducing sugars. Morphological analysis revealed predominant pellet formation (85%) with a higher surface-to-volume ratio (1.58 ± 0.69) than clumps, suggesting improved mass transfer conditions. Conclusions Rhizopus oryzae M10A1 efficiently converted starch-rich effluents into fungal biomass under statistically optimized conditions while substantially reducing nutrient load. The integration of statistical modeling and morphological control with physical and chemical parameters, its potential as a fungal cell factory within sustainable waste valorization and circular bioeconomy approaches.