Study On Co-metabolism Technology And Mechanism Of Typical Antibiotics Based On Methanotrph

Studies have shown that methanotrph can oxidize methane that functions as the only energy and carbon source,and has the strong capability to degrade a variety of refractory organics.Methanotrph can produce a highly non-specific enzyme-methane monooxygenase(MMO)-capable of promoting the transformation of various organic compounds,thus being potential to be applied into the environmental pollution control.In this study,three typical antibiotics,sulfamonomethoxine(SMM),ofloxacin(OFL)and tetracycline(TC),were selected to construct the co metabolism system of methanotrophic bacteria to achieve the effective degradation of typical antibiotics.The changes of pollutants in the inlet and outlet water were analyzed by infrared spectroscopy and three-dimensional fluorescence spectroscopy,and the microbial community structure in the system was analyzed by metagenomics technology.The functional microorganisms in the system were identified,and the main metabolic pathways in the system were analyzed.The microbial mechanism of co-metabolism and degradation of antibiotics by methanotrophs was discussed.The main conclusions are as follows.(1)The batch biofilm reactor was used to inoculate the sludge from the thickening tank of a wastewater treatment plant in Guiyang.After 23 days of operation,the daily consumption of methane was stable at about 1.1%,and the removal rate of various conventional pollutants was stable.By comparing the average concentrations of various pollutants in the effluent of the reactor under different Cu²⁺concentrations,the optimal Cu²⁺concentration was determined to be 0.5?mol·L^-1.(2)The results showed that the co-metabolism system of methanotrophic bacteria had high removal efficiency for SMM,OFL and TC.The highest removal rate of SMM,OFL and TC was 99.87%,99.31%and 99.39%,respectively.The concentration of SMM was 0.155 mg·L^-1in the biofilm of SMM co-metabolism system,2.78 mg·L^-1in the biofilm of OFL co-metabolism system,and 0.004 mg·L^-1in the biofilm of TC co-metabolism system.It shows that the removal of antibiotics mainly depends on biodegradation,and the adsorption is limited.In addition,the system has a good removal effect on all nitrogen pollutants,and the removal rate is more than 90%.(3)Infrared spectrum analysis shows that methane may be oxidized to alcohols in the system.The intermediates of SMM biodegradation may include phenols,aromatic esters,sulfones,alkanes,aromatic compounds and carbonyl compounds.The intermediates of OFL biodegradation may include aromatic esters,aromatic compounds and ketones.The products of TC may contain aliphatic compounds,phenolic compounds and aromatic compounds.Three dimensional fluorescence analysis showed that a large number of organic compounds in SMM-methane co-metabolism system were degraded,a large number of fulvic acid like compounds were produced by microbial metabolism,and glycosylated protein like compounds were accumulated.In the OFL-methane co-metabolism system,a large amount of fulvic acid like compounds were produced,and glycosylated protein like compounds in Zone V,melanospermia like compounds and lignocellulose like compounds in Zone VI were accumulated;The main substances in the effluent of TC-methane co-metabolism were glycosylated protein like substances in Zone V,fulvic acid like substances in Zone IV,melanosperm like substances and lignocellulose like substances in zone VI.(4)The results of microbial community structure analysis showed that there were methanotrph,nitrifying bacteria,nitrifying bacteria and denitrifying bacteria in each stage of the system.The main methanotrph in SMM co-metabolism system were Methylbium,Methylomonas,Methylosarcina and Methyllobulus,respectively.Methylbium may be the most important methanotrph to degrade SMM.The main methanotrph in the OFL co-metabolism system are Methylbium,Methylocystis and Methylenetera.In addition to the biodegradation of OFL,Methylenetera may also cooperate with other microorganisms to achieve nitrogen removal.The main methanotrph in the co-metabolism system of TC were Methylbium and Methylocystis,respectively.(5)KEGG pathway annotation results show that the main function of the system in each stage is metabolism.At KEGG pathway Level 3,methane metabolism and nitrogen metabolism were the main metabolic pathways in each stage of the system,which confirmed that the system constructed in this study had the function of methane oxidation and nitrogen removal.(6)Through the annotation of metagenome Module/Enzyme/KO and the analysis of microbial community diversity,we can see that:In SMM-methanotrophs co-metabolism system,Methylbium,Methylobacter and Methylosarcina are mainly involved in Ru MP cycle,while Methylocystis is mainly responsible for Serine cycle.In the OFL-methanotrophs co-metabolism system,the main methanotrophs for Ru MP cycle are Methylbium,Methylocaldum and unclassified?f??Methyloccaceae et al.Serine cycle is mainly completed by Methylocystis in the system of OFL methanotrophs co-metabolism.The co-metabolism system of TC methanotrophs is mainly composed of Methylbium,unclassified?f??Methyloccaceae and Methylotracoccus use the Ru MP cycle pathway to achieve formaldehyde assimilation.As in the co-metabolism system of methanotrophs and OFL,Methylocystis still mainly uses the Serine cycle to complete methane oxidation.The methane oxidation function of the constructed system is mainly realized by methanotrophs,and the nitrogen removal function includes nitrification and denitrification process,methanotrophs coupled denitrification process and methanotrophs independent denitrification process.