Degradation of sulphonated mono and di-azo dye as the sole carbon source in Serratia marcescens: Insights from combined wet and dry lab analysis

The high production volume of azo dyes for manufacturing and treating various consumer products leads to deleterious environmental consequences. Bacterial agents present in the environment can degrade these dyes. We, hereby, report the isolation, decolourization and degradation of a mono (Methyl orange) and di-azoic (Congo red) compound of this class of dyes by a versatile bacterium Serratia marcescens. Our isolate showed the capability of sulphonated azo dye utilization/degradation i.e. Methyl orange and Congo red usage, with no inhibitory effects on its growth in minimal medium. The calorimetric analysis showed 80.83% decolourization of Methyl orange and 92.7% decolourization of Congo red after 7 days of incubation in a shaking incubator at pH: 7 and temperature: 37 {degrees}C. An azoreductase enzyme of [~]25 KDa was detected after SDS-PAGE analysis. Quantitative and qualitative testing of the degradation phenomenon was followed by in silico analysis. Structural modeling followed by molecular docking in Molecular Operating Environment revealed numerous residues involved in binding and assisting degradation. Changes in the apo, holo, and dye-bound enzyme energy profiles were also observed. This is the first study reporting the capability of Serratia marcescens to use azo dyes/sulphonated azo dyes as the sole carbon source and the detailed computational analysis of the degradation phenomenon. We hope that these findings will be of use to environmental scientists, aid in better dye-degrading mutant creation to help craft future remediation strategies for sulphonated azo dyes.