Biotechnological conversion of olive mill wastewater and cheese whey into functional compounds with Rhodotorula...

Olive mill wastewater (OMWW) and cheese whey (CW) are two agro-industrial effluents that pose major environmental challenges due to their high organic load and potential environmental impact. This study investigates a novel valorization approach by cultivating the oleaginous yeast Rhodotorula glutinis on OMWW supplemented with CW, a nitrogen-rich dairy byproduct. Four OMWW/CW ratios (25/75, 50/50, 75/25, 100/0, v/v) were evaluated to assess their impact on microbial growth, metabolite production, and wastewater remediation. The 25/75 (v/v) and 50/50 (v/v) mixtures supported the highest biomass yields (> 5 g L⁻¹ within 3-5 days), while the 50/50 (v/v) mixture led to maximum lipid and carotenoid accumulation after 8 days. Under this condition, substantial depollution was also observed, with near-complete removal of hydroxytyrosol and tyrosol as well as significant reduction in chemical oxygen demand (COD). Carotenoids extracted from R. glutinis showed thermal stability at 60 °C and exhibited strong antioxidant and antibacterial activities. These findings demonstrate the feasibility of coupling waste treatment with the production of bioactive compounds. The proposed bioprocess valorizes two problematic waste streams into valuable microbial biomass and functional metabolites, with potential to reduce environmental impact.