Enhancing Biodegradation Efficiency of Reactive Black-5 Dye using Bacillus wiedmannii strain NAF4: Optimization of Degradation Parameters via Response Surface Methodology (RSM)

Abstract

Reactive Black 5 (RB-5) dye is extensively used in industries such as textile, paper, and leather, raising environmental concerns due to its persistence and adverse effects. This study aimed to develop efficient and eco-friendly strategies for RB-5 dye removal from industrial wastewater. RB-5 dye-degrading bacteria, namely NAF1, NAF2, NAF3, and NAF4, were isolated from soil contaminated with textile effluents. Evaluation of their decolorization potential revealed NAF4 as the most effective, achieving a decolorization percentage of 89%, followed by NAF3 and the co-culture at 75% and 73%, respectively. NAF2 exhibited the lowest decolorization potential. The isolate NAF4 showed significant production of tyrosinase and laccase enzymes, with lower quantities of lignin peroxidase and azoreductase. Phylogenetic analysis confirmed the identities of the isolates as Bacillus, Pseudomonas, Escherichia, and Citrobacter. The decolorization potential exhibited by Bacillus wiedmannii NAF4 has instigated the investigation of its capacity to secrete degradative enzymes implicated in the breakdown of azo dyes. Substantial enzyme production was observed over a duration of 192 hours. The biodegradation potential of B. wiedmannii strain NAF4 for RB-5 dye was assessed using Surface Response Optimization (SRO) modeling. The optimized conditions for RB-5 degradation were determined to be an agitation speed of 115.777 rpm, pH of 7.449, inoculum size of 12.255, and temperature of 29.74°C. The SRO model exhibited high statistical significance with an F-value of 53.30 and low p-values (<0.0001), as well as a correlation coefficient (R2) value of 0.9813. Validation studies confirmed the adequacy and precision of the model. The maximum RB-5 degradation achieved was 90.2291%. Three-dimensional plots visually represented the validated optimum conditions of variables and responses. The successful application of Response Surface Methodology (RSM) as an optimization tool highlights its effectiveness in enhancing degradation processes. This study provides insights into the potential applicability of RSM for optimizing degradation processes in various contexts. The developed eco-friendly strategies offer promising solutions for RB-5 dye removal from industrial wastewater, mitigating its environmental impact.In conclusion, the application of Response Surface Methodology (RSM) as an optimization tool proved effective in maximizing the degradation process by optimizing the degradation parameters. The success of this approach suggests its potential applicability in other contexts to enhance degradation processes.

Keywords

• Bacillus wiedmannii; Surface Response Optimization (SRO) modeling, Reactive Black 5; three-dimensional plots