Screening And Degradation Characteristics Of A Minocycline-degrading Bacterial Strain

Minocycline is a typical antibiotic among tetracycline antibiotics.It has the strongest antibacterial performance among tetracycline antibiotics.It has a wide range of clinical applications and is one of the antibiotics with the highest content in cosmetics.Its residual concentration in urban sewage is much higher than other types.Of tetracycline antibiotics.Screening special microorganisms for degradation of minocycline and clarifying its degradation mechanism provides a theoretical basis for the research and development of bioremediation and environmental treatment technologies for water bodies contaminated by tetracycline antibiotics.It has greater theoretical significance and potential application value.This study took the activated sludge samples taken from the municipal pipe network as the research object,separated and screened the microorganisms that degraded minocycline efficiently;through the study of the characteristics of the microorganisms degrading minocycline,it was concluded that the most effective microorganisms degraded minocycline.Optimal degradation conditions;the use of I-Class-VION-IMS-Qtof to capture the microbial degradation products of minocycline and infer its degradation pathways,and use the luminescent bacteria method to evaluate the degradation products of minocycline Toxicity potential;the degradation potential of minocycline degrading strains on natural tetracycline and the degradation efficiency of minocycline in actual sewage are analyzed.The main research results of this paper are as follows:(1)Through domestication and culture,a strain of minocycline-degrading bacteria DM13 was isolated and screened from municipal wastewater.The morphological,physiological and biochemical characteristics and 16S r RNA of DM13 were comprehensively analyzed,and the strain DM13 was identified as the Kluyvera intermedia.(2)By studying the influence of culture temperature,initial pH,initial concentration and other factors on the degradation of minocycline by DM13,the characteristics of microbial degradation of minocycline are obtained.The results showed that:when the temperature was 30 ~℃ and pH 7,the degradation rate of minocycline by the strain DM13 was the fastest,and the degradation rate was 93.8%in72 hours.When the initial concentration of minocycline was 75 mg/L and below,the strain DM13 could achieve rapid degradation,and the degradation rate in 72 hours exceeded 90%.The amount of bacteria inoculated and the amount of liquid loaded has no significant effect on the degradation of minocycline by DM13.(3)The luminescent bacteria method was used to evaluate the toxicity changes of biodegradation products in the process of bacterial degradation of minocycline.The results showed that the potential toxicity of minocycline solution decreased from 76.8%to 5%within 72 hours,and the toxicity of biodegradation products Lower than the parent compound.A total of 9 microbial degradation products of minocycline were captured by I-Class-VION-IMS-Qtof,with mass-to-charge ratios of 460,446,443,429,415,413,404,385,376respectively.Through the analysis of degradation products,proposed two minocycline biodegradation pathways,including deamination,demethylation,and decarbonylation enzyme-catalyzed metabolic pathways.(4)Through the degradation experiments of three natural tetracyclines,it was found that the minocycline degrading strain DM13 has the ability to efficiently degrade tetracycline,oxytetracycline and chlortetracycline.At an initial concentration of 50mg/L,a temperature of 30 ~℃,and a pH of 7,after 7 days of culture,the degradation rates of the three antibiotics all exceeded 99%.Experiments on the degradation of minocycline in the actual sewage show that bacteria can effectively reduce the concentration of minocycline in the sewage.