Persulfates radical-driven advanced oxidation: promising approach to regulate antibiotic resistance genes in composting systems

Composting serves as a pivotal technology for recycling livestock manure and reducing antibiotic resistance genes (ARGs). However, optimizing only its physicochemical properties or microbial community yields limited success in ARG removal. In contrast, persulfate radical-driven advanced oxidation processes (AOPs) have proven highly effective in eliminating ARGs. This study demonstrates that the biological heat generated during composting can activates persulfate, not only boosting the ARGs removal rate to 96% but also effectively suppressing the rebound and re-enrichment of ARGs during the compost maturation stage, maintaining a removal rate of 55%. Specifically, this approach reduces the abundances of mobile genetic elements (MGEs, e.g., intI2, IncQ-oriV) and target ARGs (tetA, tetQ, strA, sul3). The mechanisms underlying ARG removal involve two key aspects: First, strong oxidative radicals produced by persulfate activation directly oxidize and damage resistant bacteria, thereby decreasing the abundances of ARGs and MGEs. Second, persulfate primarily inhibits ARGs transmission by reshaping the bacterial community structure. In traditional composting, non-host core bacteria act as "bridges" connecting distinct microbial modules, directly facilitating inter-modular ARGs transmission. Dominant genera such as Bacillus, norank_f__Limnochordaceae, Marinimicrobium, and Tepidimicrobium mainly carry key MGEs (intI2, Tn916/1545, tnpA, IS613), which further amplify the risk of ARGs dissemination. In contrast, following persulfate addition, only Truepera is detected as a non-host core bacterium, significantly reducing cross-module ARGs transmission pathways. This study offers a promising regulation strategy for mitigating ARG-related risks during composting.