Exploring docking and aerobic-microaerophilic biodegradation of textile azo dye by bacterial systems

Abstract

Aeromonas hydrophila MTCC 1739 and Lysinibacillus sphaericus MTCC 9523 non-adapted bacteria were investigated for decolorization of 100 mg L−1 of a textile azo dye Drimaren Red CL-5B in Nutrient Broth at 37 °C, pH 8 under sequential aerobic-microaerophilic conditions for 72 h. Docking by Biosolve IT software was used to calculate docking score, identify active site residues and molecular interactions between laccase and azoreductase of both bacteria with dye. Docking score and decolorization percentage were assessed comparatively. UV–vis spectroscopy, HPLC, FTIR and GC–MS were performed for biodegradation analysis. Laccase, veratryl alcohol oxidase and azoreductase enzymes were assayed. Docking score of −31.9921, −18.1289 and −27.2792, −2.5185 kJ/mol for laccase and azoreductase while 91.96 and 88.35 % decolorization were achieved by A. hydrophila MTCC 1739 and L. sphaericus MTCC 9523 respectively. Docking studies analyzing interactions between dye and dye-degrading enzymes were in agreement with decolorization percentage. Biodegradation analysis supported biotransformation of dye into simpler products. Enzyme studies revealed high expression of dye degrading enzymes in both non-acclimatized bacteria on exposure to azo dyes compared to controls. It was suggested that A. hydrophila MTCC 1739 and L. sphaericus MTCC 9523 can be used for efficient decolorization and biodegradation of azo dye containing textile wastewater. Thus, an advanced approach consisting of an in silico preliminary screening and subsequent bacterial dye degradation is validated for an ecofriendly, economical and time-efficient bioremediation to reuse treated water.