Enhanced Strategies And Mechanisms For Improving The Biodegradation Of Phenol And Fluoranthene By Multi-species

Polycyclic Aromatic Hydrocarbons（PAHs）is a kind of persistent organic pollutants,mainly composed of two or more benzene rings.As a characteristic persistent organic pollutant with high concentration in coking wastewater,the total amount of PAHs emission accounts for about 16%in the environment.PAHs exist in each stage of coking wastewater treatment unit in a high concentration,which makes it of great significance to eliminate PAHs from coking wastewater.In some cases,the elimination of PAHs has been achieved using physical and chemical methods.However,high treatment costs,high reagent volume requirements and the generation of secondary environmental pollutants limit these traditional methods.Biodegradation is a more reliable,more environmentally friendly and more effective method.Aiming at phenol,a major pollutant in coking wastewater,and fluoranthene with the highest concentration in PAHs of coking wastewater,the enhanced degradation strategy of co-culture of strains,the co-substrate and surfactant-producing bacteria were carried out using indigenous PAHs degrading bacteria Stenotrophomonas sp.N5,phenol degrading bacteria Advenella sp.B9 and surfactant-producing bacteria Pseudomonas aeruginosa S5.It is expected to improve the degradation of fluoranthene and provide the application basis and theoretical basis for the bioenhanced degradation of PAHs in coking wastewater.In order to study the solubilization and the co-substrate effect of phenol on PAHs,the degradation of phenol and the molecular mechanism of enhancement by co-culture of Stenotrophomonas sp.N5 and Advenella sp.B9 was first carried out.The results of biodegradation experiment showed that the degradation rate of B9 to 500 mg/L phenol was9.16%within 24 hours,and the degradation rate of N5 was almost zero,while the degradation rate ofthe co-culture of N5 and B9 was 62.27%.Growth kinetics studies showed that the interaction of N5 and B9 in co-culture reduced the inhibition of phenol on microorganisms in co-culture,and co-culture significantly increased the maximum specific growth rateμ_maxand inhibition constant K_i.Based on the analysis of metabolic and functional characteristics of bacteria in co-culture and mono-culture,it was found that co-culture increased the relative expression abundance of metabolism-related pathways.The expression of three transcription factors regulating the degradation of aromatic compounds（Lys R,two-component system-response regulator and Tet R family）is conducive to the degradation of phenol.Then,phenol was used as co-substrate to study the degradation of fluoranthene in the co-culture of Stenotrophomonas sp.N5 and Advenella sp.B9.The results of biodegradation experiment showed that phenol enhanced the biodegradation of fluoranthene in the co-culture.Transcriptome analysis showed that 800 mg/L phenol triggered the up-regulation of co-culture DNA repair activity.The addition of phenol resulted in significant differential expression of3717 genes,which were mainly involved in metal ion binding andα-amino acid biosynthesis and other biochemical processes.The results showed that phenol can reduce the genotoxicity of fluoranthene by promoting DNA repair activity,and the metal ion binding and amino acid biosynthesis process are closely related to the biodegradation of fluoranthene promoted by phenol.Based on the fact that surfactants can promote the absorption and degradation of PAHs by microorganisms by enhancing the dissolution of PAHs,the surfactant-producing bacteria Pseudomonas aeruginosa S5 is introduced into the co-culture of the above-mentioned PAHs degrading bacteria N5 and phenol degrading bacteria B9 to form three different functional microorganisms co-culture（N5+B9+S5）,To study the enhancement effect and degradation characteristics of PAHs biodegradation by introducing surfactant-producing bacteria into PAHs degrading co-culture.The results of degradation experiments showed that the introduction of surfactant producing bacteria S5 enhanced the degradation of fluoranthene and phenol by co-culture（N5+B9+S5）,that S5 is an efficient degradation bacteria for catechol,which is the intermediate product of PAHs degradation.S5 reduces feedback inhibition and reduces the metabolic burden of N5 and B9 bacteria by degrading the downstream products of the PAHs degradation process,and thatA certain range of concentrations of glucose,phenol and mixed co-substrate（400 mg/L phenol+600 mg/L glucose）as a co-substrate can promote the biodegradation of fluoranthene by co-culture（N5+B9+S5）.The growth of microorganisms was evaluated by detecting OD₆₀₀,and the addition of glucose,phenol or mixed co-substrate was conducive to the growth of bacteria in the co-culture（N5+B9+S5）,and the introduction of S5 was conducive to the faster adaptation of the co-culture（N5+B9+S5）to the environment and enter the logarithmic growth phase.The metabolic activity of microorganisms was studied by electron transport system assay.The results showed that the introduction of S5 and the addition of cosubstrate improved the metabolic activity of microorganisms.It was found that the surfactant producing bacterium S5 could use single co-substrate glucose and mixed co-substrate to produce surfactants to promote the dissolution and degradation of fluoranthene during the degradation of fluoranthene in co-culture（N5+B9+S5）.The results obtained by the research show that the co-substrate of phenol and the division of labor in the co-culture of different functional bacteria can greatly improve the degradation of PAHs.Therefore,for the coking wastewater containing major pollutant phenol,the degradation of PAHs can be improved by the regulation of phenol co-substrate,the enhancement of PAHs degrading bacteria and the introduction of surfactant bacteria.