Abstract
Industrial synthetic dyes cause health and environmental problems. This work describes the isolation of 84 bacterial strains from the midgut of the Lasius niger ant and the evaluation of their potential application in dye bioremediation. Strains were identified and classified as judged by rRNA 16S. The most abundant isolates were found to belong to Actinobacteria (49%) and Firmicutes (47.2%). We analyzed the content in laccase, azoreductase and peroxidase activities and their ability to degrade three known dyes (azo, thiazine and anthraquinone) with different chemical structures. Strain Ln26 (identified as Brevibacterium permense) strongly decolorized the three dyes tested at different conditions. Strain Ln78 (Streptomyces ambofaciens) exhibited a high level of activity in the presence of Toluidine Blue (TB). It was determined that 8.5 was the optimal pH for these two strains, the optimal temperature conditions ranged between 22 and 37 °C, and acidic pHs and temperatures around 50 °C caused enzyme inactivation. Finally, the genome of the most promising candidate (Ln26, approximately 4.2 Mb in size) was sequenced. Genes coding for two DyP-type peroxidases, one laccase and one azoreductase were identified and account for the ability of this strain to effectively oxidize a variety of dyes with different chemical structures.
Highlights
Industrial synthetic dyes cause health and environmental problems
Ever since laccase-like activity was initially detected in the bacteria Azospirillum lipoferum, the use of prokaryotic cells expressing these enzymes has increased due to their potential applications[8,9,10,11,12]
The bacterial isolates were selected for this study and identified through sequencing the 16S rRNA gene
Summary
Industrial synthetic dyes cause health and environmental problems. This work describes the isolation of 84 bacterial strains from the midgut of the Lasius niger ant and the evaluation of their potential application in dye bioremediation. Genes coding for two DyP-type peroxidases, one laccase and one azoreductase were identified and account for the ability of this strain to effectively oxidize a variety of dyes with different chemical structures. Copper-enzymes can catalyze the oxidation of different natural and xenobiotic compounds, such as phenols, polyphenols, amines, substituted polycyclic aromatic hydrocarbons, pesticides and synthetic dyes, by using atmospheric oxygen Among these dyes, thiazine, azo and anthraquinone are the organic groups most commonly found, and all are recalcitrant and toxic to both the environment and humans in varying degrees[4]. The use of peroxides to remove azo dyes and other xenobiotic compounds from textile effluents is well established[23] These enzymes are presented in both eukaryotic and prokaryotic organisms[15] and new microbial peroxidases have been recently described[24]
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