Biodecolorization of azo dye using Bacillus subtilis strain CKCC isolated from compost residues

Abstract

Azo dyes are commonly used synthetic dyes found in various industrial applications globally. Recently the toxicity of these dyes has attracted the attention of researchers. The effluent from textile processes involving these dyes can have lethal consequences due to their genotoxicity, mutagenicity, and carcinogenicity. Concerns about secondary pollution from the physio-chemical treatment of textile effluents has driven research into biological treatment processes where azo dye effluent undergoes bacterial degradation. Biodecolorization has been presented in this paper as an eco-friendly alternative to physio-chemical treatment. This study focuses on the screening and isolation of effective bacteria for the decolorization of azo dyes from compost residues. Primary screening was able to isolate bacterial strains that demonstrate decolorization of azo dye effluent due to enzymatic activity surrounding each colony. 16S rRNA gene sequence analysis identified that this isolated strain had 99.35% similarity with the Bacillus subtilis strain CKCC. Under optimal treatment conditions (37.0°C; pH of 7.0; agitated at 200 rpm, fed with a 0.5% w/v yeast extract), a decolorization efficiency of 89.06 ± 1.09% was achieved after 96.0 h for an initial azo dye concentration of 20.0 mg.L-1. This compares with an efficiency of 78.95 ± 2.51% under static conditions. The B. subtilis CKCC strain has significant potential as a bioresource for effluent treatment in the textile due to its capacity to degrade azo dyes under both aerobic and anaerobic conditions.