Aeration regime modifies ligninolytic enzyme production and biodegradation of reactive black 5 by immobilized Trametes versicolor

Abstract

Removal of textile dyes from wastewater is essential from an environmental perspective. White rot fungi are effective in azo dye degradation through a process mediated by the action of specific enzymes. Three diffusers, air stone diffuser, coiled tube sparger, and circular plate diffuser, were used to evaluate the effect of the aeration regime on ligninolytic enzyme activities and the consequent degradation process of reactive black 5 in 1-L reactor cultures of Trametes versicolor immobilized in polyurethane foam. The main changes in dye structure occurred during the first 72 h with different patterns in each culture; however, after 144 h, total color removal did not have a significant difference (> 98%) between cultures. In all cases, versatile peroxidase was the enzyme with the highest titers, relative to manganese peroxidase and laccase. Dye degradation was analyzed by the changes in absorbance peaks at 596, 311, and 257 nm in the absorption spectrum of reactive black 5. A multivariate two-way ANOVA test showed that the air diffuser had a significant effect (p < 0.05) on enzyme activity and, consequently, on dye degradation. Multilinear regression analysis indicated that laccases and versatile peroxidase positively correlated with reactive black 5 decolorization and degradation, and laccases were the most efficient for decolorization.