Effects And Mechanisms Of Easy-to-biodegrade Substrate On Antibiotic Risk Elimination And Resource Conversion

The refractory organic pollutants represented by antibiotics is one of the most dangerous pollutants in water environments.However,the biological wastewater treatment as core process is generally inefficient for antibiotics biodegradation,resources recovery,etc.,which is hard to meet the actual wastewater treatment application.Easy-to-biodegrade substrate as co-substrate can provide electron donor,carbon source,and energy for microbial growth,repair metabolic function from toxic stress,optimize the community structure,increase the activity,induce the generation of specific enzymes and cofactors,promote antibiotic degradation and resource recovery significantly.However,the role and mechanism of co-substrate to microorganisms(such as bacteria and microalgae)toxicity resistance,biomass resource conversion,and the reduction of biological risk in complex natural water environments are still unclear.This study focusing on the role and mechanism of co-substrate on the risk reduction and resource conversion of antibiotics in water environment,using biochemical analysis and a variety of omics methods to analyze the regulation of co-substrate on the microorganism function,and the biological risk reduction in water environments.Firstly,L.aquatilis was used as the model bacterium,?-lactam antibiotic amoxicillin(AMO)was used as the model antibiotic,and sodium acetate(NaAC)was used as the representative co-substrate.This work reported that NaAC addition up-regulated key degrading enzymes,including ?-Lactamase,amidases,transaminase,and amide C-N hydrolase were activated,the AMO degradation and mineralization were significantly enhanced.As a result,AMO removal have a?60%increase over the control,and the microbial inhibition rate by the effluents as low as?15%.Besides,the expression levels of genes encoding the efflux pump,penicillin binding proteins,and?-Lactamase were up-regulated,and the inhibition of peptidoglycan biosynthesis was downregulated,which indicating the microbial resistance stress was enhanced,and NaAC as nutrition enhanced cell density by?170%.In the SBR system,the above contribution of the co-substrate enhanced the stability of the activated sludge,and the treatment process operated stably and efficiently for nearly 30 d.At the same time,co-substrate addition optimized the microbial community structure,promoted the degradation and mineralization of AMO,and the absolute abundance of antibiotic resistance genes(ARGs)decreased by?30%,the absolute abundance of ARGs-carrying plasmid decreased by?30%,indicating the risk of biological risks were significantly reduced.Secondly,Chlorella regularis(C.regularis)was used as the model microalgae,AMO as the model antibiotic,and NaAC as the representative co-substrate.It was found that NaAC could significantly up-regulate the key degrading enzyme genes transcription,such as hydrolase,oxidoreductase,and transferase.At the same time,the AMO degradation rate was increased by?76%,and the small molecular intermediates toxicity was significantly reduced.Genes related to glutathione and antioxidant pathway transcription was significantly up-regulated,and Chlorella's resistance stress to antibiotic toxicity was enhanced.Therefore,the specific growth rate and biomass of C.regularis increased by?77%and?36%under NaAC addition.The production of cell pigments,lipids,carbohydrates,and proteins increased significantly by?41%,?61%,?122%,and?3 4%,respectively.Thirdly,the role of co-substrate(NaAC)on the sulfamethoxazole(SMX)degradation in simulated aquifer media water environment was discussed,and the effect and mechanism of NaAC on the SMX degradation and biological risk in simulated water environment were analyzed.The results showed that the addition of NaAC could optimize the microbial community structure,regulate gene expression,enhance microbial metabolism and toxicity resistance,reduce the release of soluble microbial products,and promote the reduction of electron receptors and organic pollution risk.Thus,the co-substrate did not increase organic matter contamination risk in effluent.Whether DO or NO3-as electron receptors,SMX did not degrade with the addition of co-substrate.The total abundance of ARGs in situ medium of aquifer increased after co-substrate addition,and mainly depending on horizontal spreading,the main host of ARGs was Proteobacteria,and the main resistance mechanism was antibiotic efflux.The total abundance of ARGs in effluent of aquifer was increased,and mainly depending on vertical and horizontal spreading,the main hosts were Proteobacteria and Actinobacteria,and the main resistance mechanism was antibiotic efflux.In sum,in simulated wastewater,this study explored mechanism of co-substrate on antibiotic biodegradation and resource recovery,and the positive role of co-substrate in improving the efficiency of target antibiotic degradation and resource recovery,It was found that co-substrate mechanisms of the biological risk reduction;The positive effects of co-substrate on the reduction of organic pollutant and nitrate were demonstrated in simulated aquifer media water environment,and it is possible that co-substrate could increase the ARG abundance when antibiotics were not degraded.The results are expected to lay a theoretical foundation for the degradation of refractory organic matter,resource and energy recovery,and the elimination of biological risk.