Effects of nanoparticles on the activity and resistance genes of anaerobic digestion enzymes in livestock and poultry manure containing the antibiotic tetracycline

Taking chicken manure containing antibiotic oxytetracycline (OTC) as the research object, nano-Fe2O3 with a concentration of 300 mg/kg TS and nano-C60 with a concentration of 100 mg/kg TS as carriers were used for a 55-day sequential batch mesophilic anaerobic digestion experiment. The gas production performance, chemical parameters, antibiotic content, enzyme concentration, and resistance gene changes during anaerobic digestion were analyzed to clarify the effect of nanoparticles on anaerobic systems containing antibiotic chicken manure and provide a reliable basis for pollution reduction capacity of livestock and poultry manure. The results showed that (1) adding nano-Fe2O3 and nano-C60 promoted anaerobic gas production in chicken manure with different concentrations of OTC. The cumulative gas production from days 1 to 10 was 2,234(T5) > 2,163(T4) > 1,445(T2) > 1,289(T3) > 1,220(T1) > 1,216(CK) mL. The cumulative gas production of T4 and T5 increased by 77.29 and 83.11%, respectively. The final cumulative gas production for each group was 3,712(CK), 3,993(T1), 4,344(T2), 4,447(T3), 4,671(T4), and 4,849(T5) mL. The final OTC residue concentrations were 15.25, 20.40, 56.56, 17.67, and 16.89 μg/L, with degradation rates of 98.31, 98.80, 98.29, 99.07, and 99.11% respectively; (2) antibiotic OTC increased the activities of dehydrogenase, amylase, protease, and urease, while adding nanoparticles increased the activities of dehydrogenase and amylase, with no significant impact on cellulase, urease, and protease activities; (3) antibiotic resistance gene (ARGs) of various types were found in groups T2, T4, and T5, with the multidrug resistance gene (ARGs)-Multidrug accounting for a high proportion of 33.54, 35.63, and 37.43%, respectively, while the proportions of the other four types MLS, tetracycline, glycopeptide, and peptide ranged from 8.18 to 12.98%.