Optimization of Azo Dyes Removal by Several Eco-Friendly Bacterial Isolates from Textile Wastewater

Industrial effluents from the textile industry often contain recalcitrant azo dyes that pose severe environmental and public health risks. This study aimed to isolate and identify bacterial strains capable of biodegrading various azo dyes and to optimize environmental conditions for enhanced decolorization. Twelve bacterial isolates were obtained from different environments and identified using 16S rRNA sequencing. The capability of these bacteria to decolorize 20 distinct azo dyes was assessed in a mineral salt medium (MSM), where textile methyl red (TMR) and textile direct violet (TDV) azo dyes served as the primary carbon sources. The results showed that B. brevis, B. coagulans, L. macrolides, L. fusiformis, and B. subtilis species significantly degraded 20 diverse azo dyes in MSM, with Bacillus coagulans and Lysinibacillus macrolides achieving decolorization rates of 88.7% and 82.6%, respectively. Additionally, we optimized key growth factors, including glucose, nitrogen source, and microelement concentrations, which significantly influenced enzyme production and biomass accumulation. Enzyme assays demonstrated the activity of lignin peroxidase, laccase, and azoreductase under different nutrient conditions. The decolorization efficiencies varied with substrate type and bacterial strain, revealing unique enzymatic responses. Where B. coagulans and L. macrolides were the best isolates (p<0.01) for the biodegradation process of azo dyes. In conclusion, these study findings provide insights into sustainable and eco-friendly wastewater remediation strategies utilizing indigenous bacterial strains with high biodegradation potential.