Composting of chicken manure with biochar as a tool to reduce antibioticresistant genes pollution of the environment

Abstract

© 2020, ETA-Florence Renewable Energies. All Rights Reserved. The use of veterinary antibiotics in animal husbandry increases the distribution of antibiotic-resistant genes in the soil when it is fertilized with manure. One of the ways to reduce the spread of antibiotic-resistant genes is composting of manure. Modification of the composting process is possible using biochar, a product of thermal anaerobic decomposition of different kinds of biomass inclusive. In the present study, the fate of antibiotic-resistant genes in chicken manure composts prepared with and without addition of biochar (15% w/w) and with and without addition of antibiotic oxytetracycline (in the concentrations of 50, 150 and 300 mg kg-1) was investigated. It was revealed that biochar addition to the compost mixtures did not lead to significant alteration in temperature and moisture regimes of the process as well as in functional activity of microorganisms. Addition of oxytetracycline did not cause the alterations of composting physical parameters as well, however at high concentrations (150 and 300 mg kg-1) increase in microbial respiratory activity associated with microbial stress was observed. In all the compost mixtures, dynamics of genes encoding oxytetracycline resistance was similar: Copy number of tet(M) gene increased while that of tet(X) decreased. The introduction of biochar into compost mixtures contributed to a decrease in the copy numbers of both oxytetracycline resistance genes.