Decolorization of anthraquinone dye by Brevibacillus laterosporus R81 via polysaccharides excreted

The aim of this research was to assess the efficacy of different microbial strains in the decolorization of anthraquinone dyes. Strain R81 was obtained from a textile company's wastewater discharge for its remarkable ability to decolorize reactive blue 19 (RB19). By employing physiological and biochemical analyses, along with 16S rRNA gene sequencing, strain R81 was determined to be Brevibacillus laterosporus. After optimization, the decolorization rate achieved a peak of 86.24% over a 48-h timeframe, utilizing an initial dye concentration of 100 mg L^–1. The decolorization capacity of strain R81 was observed to be impeded by heightened levels of salt and temperature in culture solutions, yet remained unaltered when R81 cells were directly introduced into dye solutions. Furthermore, cells that were induced through prior cultivation in a medium containing RB19 demonstrated enhanced efficacy in decolorization compared to noninduced cells. Subsequent analysis indicated that the development of biofilms and the synthesis of polysaccharides by strain R81 were augmented in a concentration-dependent fashion by RB19. Nevertheless, the decolorization efficacy of R81 was impeded by the existence of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), both of which possess the capacity to eliminate polysaccharides. The decolorization capabilities were reinstated by the SDS or CTAB eluent containing polysaccharides, suggesting a reliance on the presence of polysaccharides. The employment of stepwise diethylaminoethyl (DEAE)-cellulose chromatography and decolorization experiments elucidated the importance of a specific polysaccharide in the decolorization process. This study proposes a bacteria-derived polysaccharide as a promising remedy for treating dyeing wastewater contaminated with anthraquinones.