In vitro degradation of a reactive azo dye by crude ligninolytic enzymes from nonimmersed liquid culture of Phanerochaete chrysosporium

Abstract

In vitro degradation of synthetic dyes by ligninolytic enzymes from white rot fungi is one potential way to deal with dye pollution compared with decolorization by conventional biological treatment. In this work, production of the ligninolytic enzymes was carried out at C/N ratios of 28/44 mM and 56/2.2 mM in nonimmersed liquid culture of Phanerochaete chrysosporium. In vitro decolorization of one industrial azo dye, Reactive brilliant red K-2BP, by crude lignin peroxidase (LiP) and manganese peroxidase (MnP) obtained under carbon and nitrogen limitation respectively, was examined and compared for their degradation characteristics. Both decolorization by LiP and MnP were sensitive to pH, peaking around pH 3.0, and improved at higher enzyme activities. Decolorization by LiP can be enhanced to the greatest degree (89%) with higher addition of H 2O 2 and veratryl alcohol, whereas decolorization by MnP was optimized only with a suitable dose of H 2O 2 (0.1 mM) and decreased by the addition of Mn 2+. Decolorization declined at high dye concentrations; LiP was able to decolorize a dye concentration of 60 mg/l and below to no less than 85%, and MnP of 10 mg/l to a maximum of 71%. Decolorization by LiP and MnP together was somewhat lower than that by LiP alone. It is suggested that the optimization of the H 2O 2 supply was mainly responsible for a high efficiency in continuous dye degradation by crude LiP and MnP.