Abstract
Biodegradation is found to be a promising, cost-effective and eco-friendly option for the treatment of industrial wastewater contaminated by 1,4-dioxane (1,4-D), a highly stable synthetic chemical and probable human carcinogen. This study aimed to isolate, identify, and characterize metabolic 1,4-D-degrading bacteria from a stable 1,4-D-degrading microbial consortium. Three bacterial strains (designated as strains TS28, TS32, and TS43) capable of degrading 1,4-D as a sole carbon and energy source were isolated and identified as Gram-positive Pseudonocardia sp. (TS28) and Gram-negative Dokdonella sp. (TS32) and Afipia sp. (TS43). This study, for the first time, confirmed that the genus Dokdonella is involved in the biodegradation of 1,4-D. The results reveal that all of the isolated strains possess inducible 1,4-D-degrading enzymes and also confirm the presence of a gene encoding tetrahydrofuran/dioxane monooxygenase (thmA/dxmA) belonging to group 5 soluble di-iron monooxygenases (SDIMOs) in both genomic and plasmid DNA of each of the strains, which is possibly responsible for the initial oxidation of 1,4-D. Moreover, the isolated strains showed a broad substrate range and are capable of degrading 1,4-D in the presence of additional substrates, including easy-to-degrade compounds, 1,4-D biodegradation intermediates, structural analogs, and co-contaminants of 1,4-D. This indicates the potential of the isolated strains, especially strain TS32, in removing 1,4-D from contaminated industrial wastewater containing additional organic load. Additionally, the results will help to improve our understanding of how multiple 1,4-D-degraders stably co-exist and interact in the consortium, relying on a single carbon source (1,4-D) in order to develop an efficient biological 1,4-D treatment system.
Highlights
Graduate School of Environmental Studies, Tohoku University, Sendai 980–8579, Japan; Department of Environmental Science and Resource Management, Mawlana Bhashani Science and Technology University, Santosh, Tangail-1902, Bangladesh
Three bacterial strains capable of degrading 1,4-D as a sole carbon and energy source were isolated from the stable consortium
The results of BLAST similarity searches based on the partial 16S rRNA gene sequences showed that the strains TS28, TS32 and TS43 are closely related to Pseudonocardia spp., Dokdonella spp., and Afipia spp., respectively
Summary
This study aimed to isolate, identify, and characterize metabolic 1,4-D-degrading bacteria from a stable 1,4-D-degrading microbial consortium. Three bacterial strains (designated as strains TS28, TS32, and TS43) capable of degrading 1,4-D as a sole carbon and energy source were isolated and identified as Gram-positive Pseudonocardia sp. The isolated strains showed a broad substrate range and are capable of degrading 1,4-D in the presence of additional substrates, including easy-to-degrade compounds, 1,4-D biodegradation intermediates, structural analogs, and co-contaminants of 1,4-D. This indicates the potential of the isolated strains, especially strain TS32, in removing 1,4-D from contaminated industrial wastewater containing additional organic load. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations
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