Lignocellulolytic and hemicellulolytic system of Pycnoporus cinnabarinus: isolation and characterization of a cellobiose dehydrogenase and a new xylanase

Abstract

This study investigated the lignolytic and hemicellulolytic pathways of a monokaryotic Pycnoporus cinnabarinus strain (ss3) hyperproducing laccase. The extracellular enzymes produced were identified as xylanase, laccase and cellobiose dehydrogenase (CDH). Their productions were examined using different natural substrates: cellulose, sugar beet pulp, maize, and wheat bran in order to obtain a low-cost enzymatic cocktail suitable for paper pulp biobleaching. A 92 kDa CDH, a 55 kDa 2,6-dichlorophenol indophenol (DCPIP)-reducing protein and a new 50 kDa xylanase were purified and characterized. CDH N-terminal amino acid sequence matched to the P. cinnabarinus CDH gene (AF 081574.1) as well as the 55 kDa protein representing flavin and cellulose binding domain (CBD) of that CDH. Our results suggest the existence of a highly preserved proteolytic cleavage site in this enzyme. (1) Absence of carboxymethyl-cellulase, (2) identical optimal pH (5.0) and thermal stability (up to 65 °C) of the three enzymes, (3) the possibility of varying their relative concentrations according to the medium used, and (4) a low production cost make these enzymatic cocktails suitable for paper pulp bleaching at the industrial scale.