A step into circular economy: Mycoaugmentation strategy for citrus wastewater management and value-added biocompound production

The citrus industry produces large quantities of wastewater, which are harmful to the environment if not treated properly due to their low pH, high organic matter content, residual pesticides, and genotoxic terpenes. Their physicochemical variability and the presence of antimicrobial compounds make conventional treatments less efficient and stable. Traditionally, the citrus industry has employed a 'take-use-dispose' model; however, in recent years, more sustainable strategies have been encouraged, particularly those that promote waste valorization. Although some studies have explored this perspective, few have evaluated wastewater management on real samples. In this context, mycoremediation represents a promising alternative for their handling. This study evaluated the mycoaugmentation of citrus wastewater with Pleurotus pulmonarius LBM 105 immobilized on vegetable sponge waste as a sustainable management strategy. The physicochemical characterization of citrus wastewater showed high organic matter concentration and limonene. It was determined that a 10-day treatment without prior fungal immobilization reduced COD by ≈ 93 % and overall ecotoxicity. Hence, no acclimation period or pre-inoculum was needed, simplifying the procedure and reducing treatment time. Value-added compounds, such as enzymes (endoxylanases, β-glucosidases, cellobiohydrolases, endoglucanases, and laccases) and terpineol, were also obtained during treatment. The effect on native bacteria was evaluated through metabarcoding after treatment, resulting in increased richness and diversity of bacterial communities indicating biostimulation. This research shows that mycoaugmentation with P. pulmonarius LBM 105 immobilized on vegetable sponge waste is a sustainable strategy for real citrus wastewater management, integrating wastewater treatment into value-added compound production, representing a step towards circular economy and waste revalorization. • Industrial citrus wastewater was treated with immobilized white-rot fungi. • Over 90 % of COD and ecotoxicity reduction was achieved in 10 days. • Production of oxidative and hydrolytic enzymes was established during treatments. • An increase in bacterial diversity was observed through metabarcoding.