Engineered microbial ecosystems in biofilters have been widely applied to treat odorous gases from industrial emissions. Variations in microbial community structure and function associated with the removal of odorous gases by biofilters are largely unknown. This study performed a metagenomic analysis to discover shifts in microbial community structures in a commercial scale biofilter after treating odorous gas. Our study identified 175,675 functional genes assigned into 43 functional KEGG pathways. Based on the unigene sequences, there were significant changes in microbial community structures in the biofilter after treating odorous gas. The dominant genera were Thiobacillus and Oceanicaulis before the treatment, and were Acidithiobacillus and Ferroplasma after the treatment. A clustering analysis showed that the number of down-regulated microbes exceeded the number of up-regulated microbes, suggesting that odorous gas treatment reduced in microbial community structures. A differential expression analysis identified 29,975 up- and 452,599 down-regulated genes. An enrichment analysis showed 17 classic types of xenobiotic biodegradation pathways. The results identified 16 and 15 genes involved in ammonia and sulfite metabolism, respectively; an analysis of their relative abundance identified several up-regulated genes, which may be efficient genes involved in removing odorous gases. The data provided in this study demonstrate the changes in microbial communities and help identify the dominant microflora and genes that play key roles in treating odorous gases.
Biofilters have been broadly applied to degrade the odorous gases from industrial emissions. A industrial scale biofilter was set up to treat the odorous gases. To explore biofilter potentials, the microbial community structure and function must be well defined. Using of improved biofilter, the differences in microbial community structures and functions in biofilters before and after treatment were investigated by metagenomic analysis. Odorous gases have the potential to alter the microbial community structure in the sludge of biofilter. A total of 90,016 genes assigned into various functional metabolic pathways were identified. In the improved biofilter, the dominant phyla were Proteobacteria, Planctomycetes, and Chloroflexi, and the dominant genera were Thioalkalivibrio, Thauera, and Pseudomonas. Several xenobiotic biodegradation-related pathways showed significant changes during the treatment process. Compared with the original biofilter, Thermotogae and Crenarchaeota phyla were significantly enriched in the improved biofilter, suggesting their important role in nitrogen-fixing. Furthermore, several nitrogen metabolic pathway-related genes, such as nirA and nifA, and sulfur metabolic pathway-related genes, such as fccB and phsA, were considered to be efficient genes that were involved in removing odorous gases. Our findings can be used for improving the efficiency of biofilter and helping the industrial enterprises to reduce the emission of waste gases.
BackgroundBiofilters have been broadly applied to degrade the odorous gases from industrial emissions. To explore biofilter potentials, the microbial community structure and function must be well defined. Using of improved biofilter, changes in microbial community structures and functions were investigated by metagenomic analysis. ResultsOdorous gases have the potential to alter the microbial community structure in the sludge of biofilter. A total of 90,016 unigenes assigned into various functional metabolic pathways were identified. In the improved biofilter, the dominant phyla were Proteobacteria, Planctomycetes, and Chloroflexi, and the dominant were Thioalkalivibrio, Thauera, and Pseudomonas. Several xenobiotic biodegradation-related pathways showed significant changes during the treatment process. Compared with the original biofilter, Thermotogae and Crenarchaeota phyla were significantly up-regulated in the improved biofilter, suggesting its important role in nitrogen-fixing. Furthermore, nitrogen metabolic pathway-related genes, such as nirA and nifA, and sulfur metabolic pathway-related genes, such as fccB and phsA, were considered to be efficient genes involved in removing odorous gases. ConclusionsOur findings can be used for improving the efficiency of biofilter and helping the industrial enterprises to reduce the emission of waste gas.
Dechlorination is the key step in biological degradation of dichloromethane (DCM), which is catalyzed by the enzyme DCM dehalogenase. In this study, the detailed structure and function of DCM dehalogenase in Methylobacterium rhodesianum H13 were investigated. Our results indicate that DCM dehalogenase (C1505H2255N403O430S7) is a stable hydrophilic protein localized in the cytoplasm, with an isoelectric point of 6.35. They also indicate that DCM dehalogenase is a frizzled protein with 52.43% of amino acid residues exposed on its surface, and that alpha-helices are a main structural component (53.47%). As one of the theta class glutathione S-transferases (GSTs), DCM dehalogenase presents as a dimeric structure and shows strong substrate selectivity. The catalytic tunnel radius and length of DCM dehalogenase are both 1.4 Å. Glu42 and Val43 are two of the essential amino acids in both the catalytic tunnel and catalytic pockets. The amino acid sequence of DCM dehalogenase was predicted to be homologous among various microorganisms, and its active site was conserved with eight potential sites. The recombinant DCM dehalogenase was expressed in E. coli BL21 strain. The optimum conditions for DCM dehalogenase are pH 8, temperature of 30 C and presence of Mn 2þ. All the obtained information of DCM dehalogenase will lay the foundation for further study of its structural transformation and functional improvement.
Biofilters have been broadly applied to degrade the odorous gases from industrial emissions. A industrial scale biofilter was set up to treat the odorous gases. To explore biofilter potentials, the microbial community structure and function must be well defined. Using of improved biofilter, the differences in microbial community structures and functions in biofilters before and after treatment were investigated by metagenomic analysis. Odorous gases have the potential to alter the microbial community structure in the sludge of biofilter. A total of 90,016 genes assigned into various functional metabolic pathways were identified. In the improved biofilter, the dominant phyla were Proteobacteria, Planctomycetes, and Chloroflexi, and the dominant genera were Thioalkalivibrio, Thauera, and Pseudomonas. Several xenobiotic biodegradation-related pathways showed significant changes during the treatment process. Compared with the original biofilter, Thermotogae and Crenarchaeota phyla were significantly enriched in the improved biofilter, suggesting their important role in nitrogen-fixing. Furthermore, several nitrogen metabolic pathway-related genes, such as nirA and nifA, and sulfur metabolic pathway-related genes, such as fccB and phsA, were considered to be efficient genes that were involved in removing odorous gases. Our findings can be used for improving the efficiency of biofilter and helping the industrial enterprises to reduce the emission of waste gases.
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