Evaluation of Bacterial Consortium and Optimization of Growth Parameters for Effective Decolorization of Azo Dye Reactive Red ۱۲۰

Introduction: The effluents produced as a result of the dyeing process, especially by textile industries are a major threat to sustainable environmental development. Several challenges are observed in the treatment and disposal of complex azo dyes like Reactive Red ۱۲۰ (RR۱۲۰). The aim of the present study was to optimize the dye decolorization/degradation process by bacterial consortium.Materials and Methods: The consortium consisted of three potential azo dye degraders i.e., Shewanella haliotis RDB_۱, Shewanella putrefaciens RDB_۲, and Aeromonas hydrophila RDB_۳. It was prepared in ۱:۱:۱ ratio and was named as RAR. This consortium was optimized under several nutritional and physicochemical parameters for effective decolorization of RR۱۲۰.Results: Complete decolorization of ۵۰ ppm RR۱۲۰ was achieved with ۱۰% inoculum of ۱.۰ OD۵۴۰ nm in ۳% Yeast Extract (YE) medium under static conditions in ۴ h. The optimum decolorization was observed between pH ۷-۸ and temperature ۳۰°C-۳۵°C. However, the consortium RAR showed significant activity between a pH range of ۶-۱۰, temperature ۲۵°C-۴۵°C and NaCl concentration up to ۱۰%. The electron acceptors like nitrate and nitrite salts, and electron donors like urea and casamino acids negatively affected the decolorization rate of RR۱۲۰. The sugars and organic acids failed to support decolorization in M۹ medium. However, a varying effect was observed in the ۳% YE medium. Soymeal peptone (prepared in distilled water) supported considerable decolorization but was not as effective as ۳% YE medium.Conclusions: Considering the above features and tolerance of consortium RAR to varied range of pH, temperature and NaCl concentration, it may be a suitable candidate for biodecolorization of textile effluents.