Fungal Aryl-Alcohol Oxidase in Lignocellulose Degradation and Bioconversion

Abstract

Bioconversion of lignocellulosic materials draws much interest as they are regarded as a renewable source of energy and platform chemicals. The enzyme aryl-alcohol oxidase (AAO) has been extensively studied, revealing its involvement in biodegradation of lignocellulose by several well-known white-rot fungi. Its physiological role is to supply hydrogen peroxide, from the oxidation of aromatic substrates derived from fungal secondary metabolism or lignin degradation, which can: i) be used by peroxidases to oxidise lignin; or ii) give rise, through Fenton reaction, to hydroxyl radical that is able (itself) to depolymerise cellulose and oxidise lignin. Several features make this enzyme an appealing biocatalyst that has shown its potential for industrial applications: AAO has a broad range of substrates that it oxidises by stereoselective hydride (transfer) reaction mechanism, and reduces atmospheric molecular oxygen as a co-substrate producing hydrogen peroxide.