Microbial Degradation Of Tetrabromobisphenol A In Landfill Leachate

Landfill leachate is a type of organic wastewater with high pollution level and high difficulty in treatment.Not only are there many types and concentrations of pollutants,but most of them are toxic organic compounds that are difficult to degrade.Among them,tetrabromobisphenol A has attracted much attention due to its frequent detection,high concentration,and strong endocrine disrupting effects.The biological treatment method is currently the mainstream method for treating landfill leachate due to its advantages of low energy consumption,no secondary pollution,and environmental friendliness.However,there is still a lack of profound understanding of the microbial community processes involved in the degradation of tetrabromobisphenol A,which greatly limits the development and application of its remediation technology.Aiming at the problem of microbial action process of tetrabromobisphenol A degradation in landfill leachate,this study studied the product transformation pathway,microbial community structure characteristics and microbial interaction in the process of tetrabromobisphenol A degradation through anaerobic and aerobic passage enrichment experiments,combined with amplification sequencing analysis,degradation product analysis,pure culture functional verification,genome sequencing and other technical means,Reveal the microbial mechanism of degradation of tetrabromobisphenol A.The main research findings are as follows:(1)The microbial process of degradation of tetrabromobisphenol A was revealed through generation enrichment.It was found that both aerobic and anaerobic enrichment processes significantly improved the degradation ability of tetrabromobisphenol A and maintained a high degradation rate.Analysis of the degradation products revealed that tetrabromobisphenol A may gradually generate para hydroxybenzoic acid through a series of steps such as debromination,hydroxylation,carboxylation,and decarboxylation,and undergo complete degradation.The increase in biomass also proves that the degradation products of tetrabromobisphenol A can be used by microorganisms for synthetic metabolism.Through 16 S r RNA gene amplicon sequencing and interaction network analysis,it was found that the microbial community structure and interaction network of aerobic and anaerobic enrichment processes were simplified,but the centrality and efficiency of the interaction network were improved;Among them,Pseudomonas and Comamonas are the dominant species in the community,occupying a higher number of connections in the interaction network,and their connection numbers gradually increase with the enrichment process.It indicates that Pseudomonas and Comamonas are likely to play a key role in the degradation process of tetrabromobisphenol A.(2)The key microorganisms in the enrichment community were isolated,cultured and Functional verification.A total of 52 strains including Pseudomonas and Comamonas were obtained.After physiological and biochemical identification,it was found that these strains come from 20 different genera and can grow and reproduce under conditions such as p H of 4-11,temperature of 10-40℃,and salinity of 0-8(w/v%).They can also utilize various substances as carbon sources and have strong adaptability to extreme environments.The degradation ability of tetrabromobisphenol A was tested on these strains,and Pseudomonas sp.E7 and Comamonas sp.E showed higher degradation ability of tetrabromobisphenol A.Some products from the degradation process of enriched microbial communities were also found in the degradation products of these bacteria.Further genomic analysis of Pseudomonas and Commonas revealed the presence of multiple dehalogenases(dha A)in Commonas,which may have the function of de bromination;And it has benzoic acid degradation pathways(pob A,lig ABCIJK,pca BCDFIJK),which may be related to the downstream pathway of tetrabromobisphenol A degradation.Pseudomonas does not have dehalogenase,but also has pob A and pca BCDFGHIJK,which are also related to the downstream pathway of tetrabromobisphenol A degradation.Combining microbial community analysis,degradation product analysis,and single bacterial genome analysis,it is speculated that there may be a metabolic division of labor between Pseudomonas and Commonas,which synergistically degrades tetrabromobisphenol A.Comamonas first gradually debrominates tetrabromobisphenol A,and the generated bisphenol A can be further degraded by Pseudomonas.After the propane structure breaks,(2R)-2-(4-hydroxyphenyl)-2-hydroxypropionic acid and p-hydroxyphenol are generated,which are further degraded.Pseudomonas first caused the propane structure of tetrabromobisphenol A to break bonds,generating(2R)-2-(3,5-dibromo-4-hydroxyphenyl)-2-hydroxypropionic acid and 4-hydroxy-2,6-dibromophenol,which were further degraded;These brominated degradation products can also be further de brominated by Comamonas.The degradation process of both strains goes through the benzoic acid degradation pathway,completely degrading 4-hydroxybenzoic acid and entering the TCA cycle.These processes are closely related to the energy and synthetic metabolism of cells,and may constitute an important carbon and energy source for the two strains.Therefore,it also explains that the dilution process of passage enrichment does not decrease but increase the biomass.(3)The co-metabolism culture and enhanced degradation of tetrabromobisphenol A were validated by adding different metabolic substrates and strain combinations to the six selected strains.Research has found that co-metabolism mixed culture significantly enhances the degradation ability of tetrabromobisphenol A.Especially after the addition of yeast powder,the degradation efficiency of tetrabromobisphenol A by Solidonas sp.H7 can reach over 98% within seven days;The degradation rates of tetrabromobisphenol A by mixing Flavobacterium sp.22 and 6 strains of bacteria under co-metabolic conditions of yeast powder were 88.3% and 89.7%,respectively.This fully demonstrates that the addition of metabolic substrates provides better nutritional conditions for the strain,which is conducive to rapid growth and reproduction of microorganisms and enhances the degradation effect of tetrabromobisphenol A.In summary,this paper domesticated and enriched the degradation strains of tetrabromobisphenol A in landfill leachate,analyzed the community diversity and structure during the enrichment and transfer process,and found that the core microorganisms degrading tetrabromobisphenol A were enriched.Discovered the engineering microbiome of TBBPA degradation,mainly composed of Pseudomonas and Commonas,revealing the synergistic degradation process of tetrabromobisphenol A by Pseudomonas and Commonas.Obtained strains with efficient degradation function of tetrabromobisphenol A,deeply explored the physiological and biochemical functions of these microorganisms and the degradation mechanism of tetrabromobisphenol A,and strengthened the degradation effect of tetrabromobisphenol A through strain combination and co-metabolism culture,laying a theoretical basis and providing valuable bacterial resources for the development of enhanced treatment technology of tetrabromobisphenol A in landfill leachate.