Ethanol induced response in Phanerochaete chrysosporium and its role in the decolorization of triarylmethane dye

Abstract

Ethanol was added to submerged cultures of Phanerochaete chrysosporium to enhance the production of laccase and improve the decolorization of triarylmethane dye. The addition of 10 g/l ethanol resulted in a 4.7-fold increase in laccase production, while higher ethanol concentrations caused a sharp decrease in activity. The protein content increased with the increase in ethanol concentrations; on the other hand, pellet diameter and fungal biomass wet weight decreased. The addition of ethanol to the cultivation media affected both the mycelial morphology and fungal wall permeability. Although catalase assay indicated a stress response behavior, the lipid peroxidation decreased, suggesting the presence of a protective protein compound which appears in the presence of ethanol. The partial purification of the extracellular fluid (ECF) of ethanol-amended cultures resulted in a low molecular weight fraction (<5 kDa), UV-visible spectrum for this fraction showed a single sharp peak at 356 nm under ethanol stress; this peak represents glutathione, a reductive peptide which increased 2-fold after the fungus was exposed to ethanol stress. The glutathione assay, reductive activity, and the in vitro decolorization confirm that glutathione is responsible for dye reduction (65.1%) as compared to decolorization in in vivo conditions (23.8%). The use of ethanol could improve the performance of Phanerochaete chrysosporium through laccase induction for oxidation or reductive activity depending on the concentration and mode of addition of ethanol. © 2012 Springer-Verlag and the University of Milan.