Study of Laccase Effectiveness in Decolouration and Degradation of Vinylsulphone Reactive Dyes Using Factor Analysis

Abstract

The influence of oxidoreductase (laccase) and mediator (ABTS) quantities on decolouration and degradation of four vinylsulphone (anthraquinone and azo) reactive dyes after 24 hours of treatment in laccase optimum conditions (pH 5, T = 50 °C) was studied by two-level (min, max) and three-variable (X1, X2, X3) experimental design. The factor analysis methodology was used to study the relationship between the factors (process variables) and the responses (process parameters). Four response parameters, i.e. chemical oxygen demand (YCOD), biochemical oxygen demand (YBOD5), toxicity (YHt) and decolouration (YDecol.) of treated dye solutions were assumed to be the most important parameters at identifying the degree of dye degradation and intermediates formed, respectively. The relation of laccase (X1) and ABTS (X2) quantities were the main factors influencing the effectiveness of individual dye bio-transformation (YCOD, YBOD5) at defined dye concentration (X3). In contrast, the degree of toxicity (YHt) was independent on the dye concentration applied (X3), but dependent on the chemical structure of the dye and the relation of the laccase (X1) and ABTS (X2) variables. The process variables showed no influence on the decolouration (YDecol.) confirming the laccase-mediator-substrate specificity. The results of the factor plan analysis showed limited application of the selected model at determining the significance of process variables on the response parameters of dye solutions.