Preliminary Research On Benzene Series Degrading Bacteria And Biodegradation Of Benzene Series

As the common high-toxicity organic air pollutants,benzene series are carcinogenic,teratogenic and mutagenic,which seriously endanger human health.Biodegradation gradually become the development direction of benzene series purification technology,due to its low cost,simple operation and less secondary pollution.The research works mainly involved the degradation characteristics of dominant strains,the preparation/application of compound microbial inoculum,the analysis on the microbial flora structure of benzene series degrading microorganisms.The main results were listed as follows:(1)The activated sludge and sewage collected from benzene-contaminated environments were employed as the objects.The domesticated microbial flora could tolerate high concentration of benzene series.Under 1800 mg· L-1 benzene series,the average degradation rates of benzene,toluene and styrene were above 10.4 mg· L-1· h-1.The results of highthroughput sequencing showed that the microbial diversity significantly changed along with the higher concentrations of benzene series.The dominant benzene series degrading strains were clustered under high concentration of substrate.After being domesticated 3 months,the microbial diversity were decreased,and the community center was mainly formed by Firmicutes,Actinobacteria,Proteobacteria and Bacteroidetes.Pseudomonas sp.in Proteobacteria had the highest abundance(65%)and was the dominant bacteria.(2)Four strains were screened from domesticated samples.According to the analysis results of physiological/biochemical traits and 16 S rRNA gene identification,they were named as Rhodococcus ruber SS-4,Comamonas testosteroni SS-5,Agromyces sp.SW-2 and Pseudomonas putida SW-3 respectively.R.ruber SS-4 and P.putida SW-3 have a wide degradation spectrum for organic pollutants.The degradation of styrene by R.ruber SS-4 and the degradation of benzene by P.putida SW-3 were not affected by Cu2+,Fe3+,Cr3+ etc.Under the optimal degradation conditions,the maximum specific growth rate of R.ruber SS-4 was 0.244 h-1,and the degradation rates of benzene,toluene and styrene were 65.9%,72.1%,and 82.2% respectively.The maximum specific growth rate of P.putida SW-3 was 0.195 h-1,and the degradation rates of benzene,toluene and styrene were 87.9%,81.6%,and 72.8% respectively.(3)The results of biodegradation of single and mixed substrate(benzene,toluene and styrene)showed that the degradation of benzene and toluene by R.ruber SS-4 was significantly stimulated in the presence of styrene,while the degradation of toluene was inhibited in the presence of benzene.The degradation of toluene and styrene by P.putida SW-3 was stimulated in the presence of benzene,while the degradation of toluene was inhibited in the presence of styrene.The results of transmission electron microscopy showed that the inclusions realted with substrate storage were observed in both strains,with benzene series as substrate.(4)The inoculation ratio of R.ruber SS-4 to P.putida SW-3 was identified as 1:2,the degradation rates of benzene series were higher than that of single strain,and the degradation rates of benzene,toluene and styrene were 89.8%,84.7% and 82.5%,respectively.Compared with two initial samples without addition of the compound microbial inoculum,the average degradation rate of benzene series was significantly increased by about 10% after adding the compound microbial inoculum.The compound microbial inoculum could consolidate the dominant status of the functional flora,which further establish similar bacterial composition although with different initial community structures through the synergistic effect between different bacteria.