Production and characterization of Rhizopus delemar mycelium from agroindustrial wastewaters: Influence of substrate composition and concentration

The growing demand for sustainable alternatives to conventional materials has intensified interest in mycelium-based solutions. This study investigated Rhizopus delemar mycelium production using agroindustrial wastewaters, focusing on substrate composition and concentration effects on fungal growth and material properties. Seven experimental conditions were evaluated using potato dextrose broth (PDB) at varying concentrations (33-121 g-COD/L), soybean molasses (38.5 g-COD/L), and cassava wastewater (35.3 g-COD/L). Static cultivation was performed at 25 °C for 7 days, followed by glycerin treatment and hot-pressing for characterization. PDB concentration evaluation revealed proportional biomass productivity increases from 20 to 73 g-mycelium/m 2 /d with stable consumption efficiencies (47-54% COD, 76-87% carbohydrate). Comparative analysis between PDB suppliers suggested an important role of buffering capacity, as lower alkalinity was associated with cultivation failure despite comparable COD levels. Both wastewaters successfully supported mycelium production with productivities comparable to PDB. Soybean molasses achieved 18.4 ± 0.3 g-mycelium/m 2 /d productivity, while cassava wastewater exhibited distinctive behavior with highest utilization efficiencies (79% COD, 88% carbohydrate consumption) and pH neutralization. Material characterization revealed elastic moduli of 60-205 MPa and tensile strengths of 1.20-2.05 MPa, comparable to elastomeric materials. These results indicate that R. delemar is a promising candidate for sustainable biomaterial production from agroindustrial wastewaters, suggesting potential benefits of combining waste valorization with renewable material generation.