Research On Biofilm Enrichment Characteristic Of Hydrogen-based Biofilm Reactor Based On Microbial Quorum Sensing

Hydrogen-based membrane biofilm reactor(MBf R)can efficiently remove oxidative pollutants and is a technology with broad application prospects.However,the slow growth and metabolism rate of hydrogen autotrophic microorganisms result in a slow start-up speed of the reactor membrane,which also limits the large-scale application of the reactor.Therefore,it is crucial to understand the mechanism of biofilm formation and solve the problem of slow film formation from the source.Quorum Sensing(QS)is a means of communication between microorganisms and is considered closely related to the formation of biofilms.Based on QS theory,this study focused on the biofilm enrichment in the process of removing nitrate by H₂-MBf R.Through the identification and analysis of 11 quorum sensing molecules(AHLs)in the reactor system(liquid phase,biofilm layer),the dominant type of AHLs associated with biofilm formation.Finally,metagenomic sequencing technology was used to analyze and discuss the microbial population structure and QSrelated organisms in the reactor.This research providesa theoretical basis and technical support for rapid start-up and stable and efficient operation of the H₂-MBf R process.The main findings are as follows:(1)Build a reactor system,conduct AHLs detection during the initial period of operation and during the stable period,and determine the dominant AHLs type.Signal molecules with high content in the early stage of biofilm include C₄-HSL(0.13?g/L),C₆-HSL(0.17?g/L),C₁₄-HSL(12.23?g/L),3-oxo-C₁₄-HSL(0.15?g/L),C₁₂-HSL(0.13?g/L),C₁₀-HSL(0.13?g/L),each AHLs changes in the mature and stable stage of biofilms,the dominant types are C₄-HSL,C₆-HSL,C₇-HSL,C₈-HSL,the contents are 0.45?g/L,0.37?g/L,0.16?g/L,0.61?g/L,respectively.(2)Analyze the content of biofilm components at different operating stages,and compare the correlation between AHLs and EPS(extracellular polymers)and SMP(soluble metabolites).In biofilms,the types of AHLs that can promote EPS secretion are C₄-HSL,C₈-HSL,C₁₂-HSL,3-oxo-C₁₀-HSL;SMP content is extremely correlated with 3-oxo-C₁₀-HSL and C₈-HSL Significant(P<0.01).In water samples(in suspension),the AHLs that simultaneously promote the production of SMP and EPS are C₄-HSL,C₈-HSL and3-oxo-C₁₀-HSL.(3)Using the metagenomic sequencing method,the characteristics of microbial community and QS-related organisms in biofilm were discussed.In the initial stage of reactor operation,the main strains are Methanobacterium,Mycobacterium and Thaurea,and the main dominant strains are Candidatus,Accumulibacter,Hydrogenophaga,and Methylibium in the stable phase.Rhodopseudomonas is the QS microorganism that produces AHLs.In additon,6genera of other types of QS microorganisms were found,namely Vibrio,Klebsiella,Yersinia,Escherichia,Enterobacter and Photorhabdus.(4)Explore the influence of AHLs on H₂-MBf R biofilm components.A shake flask was used to simulate the operating conditions and growth environment of the reactor,and the seven dominant types of AHLs were added to analyze the changes in nitrate removal rate,EPS,and SMP.The effects of the five AHLs on the reactor were clarified.The AHLs that promote the growth of biofilms include C₄-HSL,3-o-C₁₀-HSL and C₈-HSL,which increase the EPS production rate by 14%,4%and 23%,respectively,and increase the secretion rate of SMP by 184%,149%and 218%.These three signal molecules can increase the growth rate of biofilms;AHLs that signi ficantly inhibit the growth rate of biofilms include C₁₄-HSL and 3-o-C₁₄-HSL.