Bacterial cell lysis induced by pre-acidification greatly promoting the degradation of carried antibiotic resistance genes in zero-valent iron activated Fenton-like processes

Zero-valent iron (ZVI) activated Fenton-like processes have been proposed to inactivate ARB that carry diverse antibiotic resistance genes (ARGs) in wastewater, whereas they exhibit very low capacity of degrading ARBcarrying ARGs. Our previous study has revealed that pre-acidification can make cell inactivation and lysis. Thus, the present study investigated the effect of pre-acidification on the inactivation of a multi-drug resistant bacterium Pseudomonas putida MX-2 and the simultaneous degradation of carried seven ARGs by ZVI/H2O2 and ZVI/PDS processes. Results showed that the pre-acidification of bacterial solution to acidic pH greatly promoted the degradation of carried ARGs from 0.14 to 0.17 logs to 2.48-2.97 logs at the meanwhile of almost completely inactivating P. putida MX-2 in both ZVI/H2O2 and ZVI/peroxydisulfate (PDS) processes. Moreover, the preacidification seriously lysed the bacterial cells, released the carried ARGs into the extracellular environment, and facilitated the degradation of extracellular ARGs (e-ARGs) by the generated radicals. During the degradation of the resultant e-ARGs, they were fragmented to short fragments by ZVI/H2O2 and ZVI/PDS processes. The treatment of real wastewater containing P. putida MX-2 further validated the promoting effect of pre-acidification on the degradation of carried ARGs. Therefore, it is extremely crucial to lyse the cells of ARB efficiently via acidification or other methods to promote the degradation of carried ARGs greatly, which may also be applicable for other advanced oxidation processes to reduce antibiotic resistance in wastewater effectively.