Assessing the safety of thermally processed penicillin mycelial dreg following the soil application: Organic matter's maturation and antibiotic resistance genes.

To degrade the residual penicillin G in penicillin mycelial dreg (PMD), thermal treatment was used as a pretreatment for practical disposal. Given that the characteristics of treated-PMD aren't adequately clear, a lab-scale experiment was conducted to verify its safety assessment for land application under the following points: (i) variation of penicillin G residue (ii) maturity of organic matter (OM) (iii) phytotoxicity (iv) abundance of antibiotic resistance genes (ARGs). A high-throughput quantitative polymerase chain reaction (HT-qPCR) method was used to perform an overall investigation of soil ARGs. The results show that heat treatment effectively degrades 98% of penicillin in PMD within 120 min. After thermal treatment, the treated-PMD was applied to soil. The original penicillin level was considerably lower and completely degraded within 4 days. Variation of germination index (GI) implied that the created phytotoxicity was significantly reduced. Furthermore, compared with PMD, the addition of treated-PMD didn't cause enrichment of soil ARGs in diversity and abundance. Therefore, heat treatment can be considered as an effective pretreatment for PMD practical application.