Degradation Of Oxytetracycline And The Abundance ARGs In Microbial Fermentation System

The enlargement of livestock and poultry farming scale has brought about economic benefits and serious environmental pollution problems at the same time.In recent years,there have been many reports on the removal efficiency and mechanism of antibiotics residues in livestock and poultry manure during composting,but few reports on the degradation of antibiotics residues and the changes of resistance gene abundance in microbial fermentation bed.Therefore,this study focused on the treatment of pig wastes by heterotopic fermentation bed with oxytetracycline and its resistance genes,focusing on exploring the effect of heterotopic fermentation bed on pig wastes,analyzing the degradation of antibiotics,microbial population changes and the rule of resistance gene removal.The influence of antibiotic degradation and the variation of resistance gene abundance in microbial fermentation bed was clarified,which promoted the popularization and application of microbial fermentation bed technology,and was of great significance to the maintenance of animal and human health and the protection of ecological environment.It was found that oxytetracycline could be effectively degraded by heterotopic fermentation bed with oxytetracycline,and the degradation rate reached 82% after 3 days.At 73 days,the content of oxytetracycline in fermentation bed was 5mg/kg,which was lower than the residual concentration of oxytetracycline in composting treatment.The addition of oxytetracycline caused changes in the number of microorganisms and physicochemical indexes in the fermentation bed.Adding oxytetracycline could increase the quantity of OTU,increase the microbial richness of filler,change the dominant species and community structure of microbial population.Before adding oxytetracycline,there were mainly three dominant species: Firmicutes,Actinobacteria and Proteobacteria.After adding oxytetracycline,Firmicutes occupied the main position,while Bacteroidetes,Gemmatimonadetes and Chloroflexi had some non-significant growth.The heterotopic microbial fermentation bed has a good removal effect on oxytetracycline resistance genes,the removal rate can reach 99% in 73 days;tetQ,tetB,tetC all show a gradually decreasing trend,while tetW,tetO,tetM show a trend of increasing first and then decreasing;tetB,tetC,tetQ and OTC concentration show a significant positive correlation,and environmental factors such as total nitrogen,water content and organic matter,such as resistance genes.Removal has an impact.In addition,compared with the heterotopic fermentation bed filled with corn straw,the temperature of pig heterotopic fermentation bed filled with rice husk and coconut husk powder was 25-54 degree C,the pH value was 7.6-8.9,and the water content was between 44% and 64%,which was closer to the optimum range of aerobic fermentation.At 73 days,the pH,TN,TP,TK and organic matter of the two kinds of fermentation bed fillers met the national organic fertilizer standard.The temperature of heterotopic fermentation bed ranges from 53-67 degree C and pH from 7.47 to 8.56.The changes of the temperature and pH of heterotopic fermentation bed are relatively small,which provides a more stable living environment for thermophilic bacteria and promotes the metabolism process of microorganisms and the decomposition of organic matter.In summer,the temperature of the in-situ fermentation bed was higher,which resulted in the average weight of pigs being 30 kg lower than that of the heterotopic fermentation bed.The absorption coefficients of pig wastewater and feces in the heterotopic fermentation bed filled with poplar leaves,corn straw and coconut shell powder were 2.24 and 1.42,respectively,which were slightly higher than those in the heterotopic fermentation bed filled with corn straw under the same conditions.This indicated that the heterotopic fermentation bed had better treatment capacity of breeding wastes and slightly different treatment capacity due to different materials.This study clarified the degradation of oxytetracycline residues and the variation of resistance gene abundance in microbial fermentation bed,and clarified that microbial fermentation bed technology is a low-pollution emission and Eco-environmental pollution control model for aquaculture.The relevant research conclusions provide suggestions for the popularization and application of microbial fermentation bed technology and theoretical basis for pollution prevention and control in livestock and poultry breeding industry.