Abatement of antibiotics and antimicrobial resistance genes from cephalosporin fermentation residues by ionizing radiation: From lab-scale study to full-scale application

Abstract

The antibiotic fermentation residues derived from the production of a cephalosporin precursor, deacetyloxy cephalosporin C (DOCPC), classified as “Hazardous Waste” in China, was treated by ionizing irradiation from lab-scale experiment to full-scale application. From bench-scale experiments, it was observed that gamma irradiation exhibited a little higher effect to decompose DOCPC than electron beam (EB) irradiation. The removal efficiency of DOCPC reached 97.5% by γ-ray irradiation and 92.9% by electron beam (EB) irradiation at the same absorbed dose of 50 kGy. The rate constant of DOCPC degradation was 1.4 fold (in the fermentation residues) and 1.1 fold (in the supernatant) higher by γ-ray irradiation than that by EB treatment. Oxidation by ·OH was mainly responsible for DOCPC decomposition. The beta-lactam resistance gene cphA was found in the raw DOCPC fermentation residues, with the absolute and relative abundance of 5.1 ⅹ 103 copies/mL and 0.15%, respectively. After 50 kGy of ionizing irradiation, the relative abundance of cphA was abated by 57%. The full-scale EB accelerator was constructed to treat the fermentation residues continuously with the capacity of 100–120 m3/d. During 2 months of operation, the removal efficiency of DOCPC was in the range of 61.5 ± 10.3% with EB intensity of 49 mA, roller frequency of 10 Hz and energy of 1.5 MeV, and it increased to 75–84% after the second irradiation. Ionizing radiation is a promising alternative to treat the antibiotic fermentation residues and the development of electron accelerator and irradiation vessel specific for the fermentation residues treatment is critical for improving the efficiency of industrial application.