Application of a mixture design to optimize textile azo-dye decolorization using a bacterial consortium

Abstract

Textile wastewaters (TWWs) are characterized by high salinity and alkaline pH. Bioremediation using fungi were proved in many cases as inefficient tools to treat such effluent, giving the relay to haloalkaliphilic bacteria. Here, three extremophilic strains namely Halomonas desertis G11, Kocuria rosea BU22S and Microbaterium trichothecenolyticum TL13 have been selected to conduct textile dye decolorization experiments. The effect of different combinations of these strains was studied by a mixture design (MD) to assess Tubantin Brown GGL (TB GGL) color removal during species growth under optimzed conditions of dye concentration (100 mg/L), pH (9), salinity (5%), inoculum size (5%) and time (10 days). A remarkable decolorization was observed using mono and mixed cultures. Using the NemrodW software, the optimisation calculations were performed to find an optimum mixture proportions for maximum azo dye decolorization. High regression coefficients R2, between the variables and the response indicated excellent evaluation of experimental data by the polynomial regression model. The highest color removal (about 92%) was obtained with binary mixture composed by H. desertis G11and M. trichothecenolyticum TL13 and it was in close agreement with the estimated response value (93%). This finding shows a biotechnological potential of haloalkaliphilic bacteria in TWWs treatment.