From Screening to Laboratory Scale-Up: Bioremediation Potential of Mushroom Strains Grown on Olive Mill Wastewater

Olive mill wastewater (OMW) is a phenol-rich effluent with high organic load, posing significant environmental disposal challenges in the Mediterranean countries. This study evaluated the bioremediation and valorization potential of OMW by eleven edible and/or medicinal fungal strains (Agrocybe cylindracea, Lentinula edodes, Pleurotus sapidus, Pleurotus sajor-caju, Flammulina velutipes, Ganoderma adspersum, Tuber aestivum and Tuber mesentericum). Firstly, screening for mycelial growth on agar media with commercial glucose and OMW (concentrations from 0 to 50%, v/v) revealed a strain-specific tolerance to phenolic toxicity. Although all tested strains could grow on OMW-based media, G. adspersum, T. mesentericum and T. aestivum presented the highest mycelial growth rates (Kr), exceeding 10 mm/day at elevated OMW levels (50%, v/v). Based on screening outcomes, seven strains were selected for further evaluation under static liquid fermentations in media with 15 and 35% (v/v) OMW. Growth kinetics, substrate consumption, phenolic removal, decolorization capacity, intracellular polysaccharide (IPS) and total lipid content were assessed. Tuber spp. and G. adspersum exhibited the highest tolerance to phenolic compounds, producing biomass exceeding 15 g/L at 35%, v/v OMW. Maximum IPS production reached up to 46.23% (w/w), while lipid content exceeded 15% (w/w) of dry biomass in F. velutipes and T. mesentericum, indicating an oleaginous microorganism-like behavior. Phenolic removal surpassed 80% in most cases, demonstrating efficient enzymatic degradation. Decolorization efficiency varied between strains, but remained above 70% for L. edodes, G. adspersum and F. velutipes. These findings highlight the potential of edible and/or medicinal fungi to simultaneously detoxify OMW and produce biomass and high-value metabolites, supporting a sustainable, low-cost agro-industrial waste management aligning with circular bioeconomy principles.