Treatment of a steroid fermentation residue using ionizing radiation: steroid degradation and biotoxicity abatement

Steroid hormones, particularly the persistent 9-hydroxyandrostenedione (OHAD) in fermentation residues, pose significant environmental concerns due to their environmental persistence, bioaccumulation potential and ecotoxicity. This study demonstrates that ionizing radiation, a unique form of advanced oxidation, effectively degrades OHAD. At 50 kGy, OHAD removal efficiency reached 96 % and 88 % when the initial concentration was 331 mg/kg and 606 mg/kg, respectively. The bacterial count decreased by 2 log orders of magnitude at 25 kGy, and complete inactivation achieved at 50 kGy. Wheat seed germination and root elongation tests demonstrated a significant reduction in biotoxicity after irradiation. The steroid fermentation residues, could support the growth of acidogenic bacteria, particularly Firmicutes phylum and Lactobacillus genus, and potentially pathogens, such as Escherichia-Shigella, Enterococcus, and Enterobacteriaceae, while their abundance decreased after 50 kGy of irradiation. Ionizing radiation effectively mitigates environmental risks from steroid wastes through simultaneous contaminant degradation, microbial inactivation, and toxicity and pathogens reduction.