Biological decolorization of aniline blue by a novel bacterial strain isolated from the feces of the giant panda (Ailuropoda melanoleuca)

Abstract Introduction Microbial degradation of synthetic dyes has emerged as a sustainable and efficient green bioprocess for the remediation of dye-contaminated wastewater, offering great potential for industrial-scale treatment of environmental pollutants. Purpose This study explored the biodegradation potential of the triphenylmethane dye aniline blue (AB) using a novel gut-derived microbial strain isolated from giant panda feces, focusing on efficiency and associated mechanisms across defined environmental conditions. Results The isolated gut microbial strain was taxonomically classified as Brevibacillus parabrevis through 16S rRNA gene-based phylogenetic analysis and whole-genome sequencing. Systematic optimization of key physicochemical parameters—including pH (5–8), initial dye concentration (50–300 mg/L), inoculum size (0.5%–5%), and temperature (25–40 °C)—was conducted to determine conditions for maximal AB decolorization. The strain demonstrated broad pH tolerance (5–8), sustained growth at high dye concentrations (300 mg/L), and efficient dye removal. Optimal decolorization efficiency (90%–93%) was achieved at pH 6–7, with an inoculum size of 1%–5%, temperatures between 30–40 °C, and dye concentrations ranging from 50–300 mg/L. Genomic, metabolic, and enzymatic analyses identified dye-decolorizing peroxidases (DyPs) as key catalysts in the initial degradation of AB. The resulting intermediates were further converted into aromatic compounds, which likely entered the tricarboxylic acid cycle for full mineralization. Conclusions Brevibacillus parabrevis exhibited strong potential as an efficient biocatalyst for the environmentally sustainable treatment of triphenylmethane dyes, offering a promising approach for industrial treatment of synthetic dye pollutants.