Effect Of SBR On Treatment Of Fosfomycin Wastewater And Its Microbiological Analysis

Fosfomycin,as a broad-spectrum antibiotic,has good antibacterial activity against both Gram-positive and Gram-negative bacteria.The traditional biological treatment process is susceptible to be inhibited by fosfomycin,resulting in low removal efficiency or even system collapse.In order to improve the efficiency and stability of the biological treatment,it is necessary not only to pay attention to the treatment efficiency of biological system and the properties of sludge,but also to the dynamic changes of microbial community.In this study,the SBR reactor was used to treat fosfomycin simulated wastewater,the degradation effect was evaluated,the functional species and key genes of fosfomycin degradation were identified,and the biodegradation mechanism of fosfomycin was explored,so as to provide theoretical basis for the practical engineering application.A method for simultaneous determination of fosfomycin and diol by ion chromatography was developed to characterize the target pollutants more easily and efficiently.The retention time of fosfomycin and diol were 9.7 min and 8.5 min,respectively.Fosfomycin has a good linearity in the range of 0.0025～0.1 mmol/L,and that of diol has a good linearity in the range of 0.02～1 mmol/L.The method has high specificity,simplicity and reliability,can meet the requirements of rapid,high precision and low detection limit.The SBR reactors constructed with acclimated sludge can stably remove up to1000 mg/L fosfomycin simulated wastewater,and the removal efficiency is up to 99.6%,but 16 days of shocking adaptation period was consumed.When the concentration of fosfomycin sodium reached 500 mg/L,the nitrifying bacteria were significantly inhibited,which indicated the inhibition of nitrification.The biological system degraded fosfomycin and acetate simultaneously when the influent contained both readily degradable carbon sources and fractory components.Flow cytometry can be used to quantify the cell viability and bacterial population of activated sludge and track the dynamic change of microbial community structure.The live bacteria in SBR system was stable between 55.3%and 86.5%,indicating the system operated relatively stably.Mixed carbon sources system can significantly enhance cell viability and bacterial population,and make activated sludge system more efficient and stable.The function of the sub-communities could be induced by the correlation analysis between the relative abundance of microbial sub-communities and the amount of pollutants removed.G7 and G8 microbial communities mainly play a role in the recovery period after high impact load,G6,G3 and G4 microbial communities were mainly involved in the degradation of fosfomycin.The influent carbon source significantly affected microbial community structure of SBR system.Driven by the selection of specific carbon sources,the species abundance and diversity gradually decreased,and the community structure and function were gradually differentiated.Combined with the analysis of species abundance and different species,Hydrogenophaga sp.,Comamonadaceae bacterium and uncultured bacterium＿g＿Ferruginibacter were presumed to be involved in high concentrations of fosfomycin degradation,Ralstonia sp.and Acidovorax sp.were presumed to be involved in low concentrations of fosfomycin degradation.K00799（glutathione-S-transferase）was highly expressed in fosfomycin degrading bacteria,which was presumed to be the key gene for fosfomycin degradation.Therefore,it is proposed that the first step of fosfomycin biodegradation is the nucleophilic addition of glutathione and fosfomycin catalyzed by glutathione-S-transferase.It is consistent with the prediction of active site of fosfomycin based on DFT.In the subsequent degradation process,C-P bond breaks and PO₄^3- is generated.