Biodegradation of Congo Red and Orange G by Bacillus cereus from the Saida Dumpsite: Experimental and In Silico Evidence

Understanding the potential mechanisms of bacterial azo dye decolorization remains a challenge due to a limited understanding of the exact stereochemical forces guiding enzyme–substrate interactions. This study addresses these interactions by evaluating the in silico binding architectures of Orange G (OG) and Congo Red (CR) against the Bacillus-derived azoreductase model AzrA (PDB ID: 3W77). Computational modeling predicted favorable thermodynamic properties within the calculated active site, yielding binding energy scores of −8.17 kcal/mol for CR and −6.63 kcal/mol for OG. These simulations identified hydrogen-bonding and aromatic π-π interactions within the predicted binding pocket. These predictions suggest potential enzyme–dye association but do not demonstrate catalytic activity or azo-bond cleavage. Independently, Bacillus cereus BC WW Saida achieved an 81% decolorization of OG within 144 h and a 70% reduction in CR within 96 h. High-performance liquid chromatography (HPLC) indicated chemical transformation, demonstrating a significant decrease in primary dye peaks alongside the emergence of novel intermediate peaks at 254 nm. Rather than definitively establishing a metabolic pathway, these outcomes deliver preliminary structural models of azoreductase-substrate affinities, offering a useful framework for the comparative evaluation of microbial catalysts for industrial effluent purification.