Isolation and characterization of a novel strain of Rhizopus arrhizus for effective biodegradation and detoxification of zearalenone.

Zearalenone (ZEN) is a prevalent estrogenic mycotoxin in cereals and feed, posing significant risks to feed safety and animal health. In this study, a food-associated filamentous fungus, Rhizopus arrhizus MNQW, was isolated from traditional Xiaoqu and systematically evaluated for its ZEN biodegradation efficiency and application potential. Under mild fermentation conditions, the strain removed over 98% of 5 mg/L ZEN in minimal salt medium within 36 h. Subcellular fractionation and inhibitor assays indicated that ZEN degradation was mainly mediated by heat- and protease-sensitive intracellular enzymes. LC–MS/MS analysis detected only trace and transient α-zearalenol, with no accumulation of estrogenically active intermediates. In vitro assays using MCF-7 and HepG2 cells confirmed that the final degradation products showed neither estrogenic activity nor cytotoxicity. In solid-state fermentation of ZEN-contaminated maize flour, Rhizopus arrhizus MNQW achieved approximately 97% toxin removal within 36 h while improving nutritional quality, including increased crude protein, vitamin B2, folate, and beneficial fatty acids. Whole-genome analysis further identified multiple oxidoreductase- and hydrolase-encoding genes potentially involved in ZEN biotransformation. Collectively, these findings suggest that Rhizopus arrhizus MNQW has potential as a relatively safe and effective microbial candidate for the detoxification and value-added bioprocessing of ZEN-contaminated feed materials.