From antibiotic mycelial residue to safe organic fertilizer: Synergistic removal of pleuromutilin and antibiotic resistance genes via alkaline-thermal pretreatment and composting

Pleuromutilin mycelial residue (PMR), a by-product of tiamulin production containing residual antibiotics, is listed in the Chinese Directory of National Hazardous Wastes. Aiming at the detoxification and resource utilization of PMR, this study examines a full-systematic process involving alkaline thermal pretreatment, aerobic composting, and soil risk evaluation. Under optimized pretreatment conditions, the release of water-soluble organic matter increased by approximately 72.3%, while 51.5% of residual pleuromutilin was simultaneously degraded, enhancing substrate biodegradability. Following aerobic composting, pleuromutilin in fertilizer were further reduced to below 50.0 μg/kg, and the fertilizer exhibited higher nutrient content (8.1%) than a selected commercial fertilizer (5.1%). Pot experiments showed that application of the PMR-derived compost improved soil organic matter, available nitrogen, and enzyme activities without adversely affecting soil quality. Quantification of ARGs indicated no enrichment of targeted ARGs in soil amended with this fertilizer, suggesting low ecological risk under the investigated conditions. Soil microbial diversity analysis indicated that the application of bacterial residue fertilizer caused weaker environmental disturbances and maintained high community structure similarity. Overall, this study provides a comprehensive strategy for PMR valorization with controlled antibiotic and antibiotic resistance risks