Enhanced decolorization of congo red and methyl orange using Bacillus haynesii ING6: an optimization study using...

The discharge of synthetic azo dyes such as Congo Red (CR) and Methyl Orange (MO) from textile industries poses severe threats to aquatic ecosystems and human health due to their toxicity, stability, and resistance to conventional treatment methods. The study investigates the decolorization potential of a thermophilic bacterium, Bacillus haynesii ING6, isolated from Tuva-Timba hot springs, for simultaneous degradation of CR and MO. Optimization of process parameters, including pH, dye concentration, temperature, inoculum size, and sugar concentration, was performed using Response Surface Methodology (RSM) with Central Composite Design (CCD). The quadratic polynomial models developed for both dyes were statistically significant, with high coefficients of determination (R² = 0.9939 for CR and 0.9952 for MO) and non-significant lack-of-fit values. ANOVA confirmed that pH, dye concentration, and temperature were the key factors significantly influencing degradation efficiency. Response surface plots revealed strong interactive effects among parameters, with maximum degradation efficiencies achieved at pH 8, 50 mg/L dye concentration, 55 °C, 5% inoculum, and 3% sugar. Under optimized conditions, Bacillus haynesii ING6 accomplished 95.23% CR removal and 96.29% MO removal. These findings provide the first report of azo dye degradation by Bacillus haynesii ING6, highlighting its potential as a sustainable bioremediation agent for textile wastewater treatment.