Microaerophilic degradation of sulphonated azo dye – Reactive Red 195 by bacterial consortium AR1 through co-metabolism

• AR1 proficiently decolourize 1500 mg/L RR195 with minimum nutrient requirement.
• It demonstrated broad substrate specificity in presence of high salt concentration.
• Degradation profile of RR195 showed presence of lower molecular weight compounds.

The textile and dye industries are considered as one of the foremost sectors that pollutes environment. Technologies employing biological methods showed promising approach to remediate sites polluted with dye and dye intermediates. Bacterial consortium AR1 developed through culture enrichment method was comprised of four distinct bacterial strains. The synergistic metabolic activities of AR1 led to complete decolourization of monoazo dye Reactive Red 195 within 14 h under microaerophilic environment. The co-metabolic decolourization of Reactive Red 195 by consortium, in presence of maltose and proteose peptone (0.1%, w/v, each) in minimal medium, easily reduced Reactive Red 195 (100 mg/L) for five consecutive cycles without any replenishment of nutrient. The maximum decolourization was observed at pH 8.0 and 40 °C. The consortium was acclimatized to decolourize Reactive Red 195 at higher concentration (2000 mg/L) even under high salt concentration (1 M NaCl). Consortium exhibited broad substrate specificity where it decolourized 15 structurally different dyes and more than 50% decolourization was observed in a medium containing mixture of dyes. The degradation products analyzed using FTIR, HPTLC and 1H NMR revealed the formation of 2-amino-naphthalene, 1-amino-benzene and 1-nitro-benzene. Thus the ability of bacterial consortium for simultaneous decolourization and degradation of azo compounds signifies its potential application in dye remediation.