Response surface methodology mediated optimization of decolorization of azo dye amido black 10B by Kocuria kristinae RC3

Abstract

The bacterium, Kocuria kristinae RC3 capable of decolorizing sulfonated azo dye, amido black 10B was isolated using enrichment technique and identified by 16s rRNA gene sequencing. A maximum decolorization of 74.19% was achieved in the mineral salt medium at 37 °C and 24 h of incubation time. Effect of medium components and process conditions on decolorization efficiency was studied using response surface methodology involving a central composite design. Further, the interactions between the process conditions, i.e., pH, temperature, cell mass, dye concentration, and medium components, i.e., glucose, yeast extract, K₂HPO₄ and (NH₄)₂SO₄ concentration were modeled and investigated. The predicted values were found to be in good correlation with experimental values. The process conditions were optimized which resulted in 93.0% dye decolorization by the bacteria in 24 h. The optimized process conditions for maximum decolorization of amido black 10B by the bacterium were pH (7.4), cell mass (2.9 g/L), temperature (35.3 °C) and dye concentration (137.46 mg/L) in 24 h. The optimal medium conditions for maximum decolorization determined by RSM were glucose (3.17 g/L), yeast extract (1.05 g/L), K₂HPO₄ (1.66 g/L) and (NH₄)₂SO₄ (1.06 g/L). Under these conditions, maximum decolorization of 96.83% was achieved in 24 h. The results demonstrated that K. kristinae RC3 could be employed for the treatment of amido black 10B contaminated wastewater/effluents.