초록
<P><B>Background</B></P><P>Cellobiose dehydrogenase (CDH) is an extracellular hemoflavoenzyme produced by lignocellulose-degrading fungi including <I>Pycnoporus cinnabarinus</I>. We investigated the cellulolytic system of <I>P. cinnabarinus</I>, focusing on the involvement of CDH in the deconstruction of lignocellulosic biomass.</P><P><B>Results</B></P><P>First, <I>P. cinnabarinus </I>growth conditions were optimized for CDH production. Following growth under cellulolytic conditions, the main components secreted were cellulases, xylanases and CDH. To investigate the contribution of <I>P. cinnabarinus </I>secretome in saccharification processes, the <I>Trichoderma reesei </I>enzymatic cocktail was supplemented with the <I>P. cinnabarinus </I>secretome. A significant enhancement of the degradation of wheat straw was observed with (i) the production of a large amount of gluconic acid, (ii) increased hemicellulose degradation, and (iii) increased overall degradation of the lignocellulosic material. <I>P. cinnabarinus </I>CDH was heterologously expressed in <I>Pichia pastoris </I>to obtain large amounts of pure enzyme. In a bioreactor, the recombinant CDH (rCDH) expression level reached 7800 U/L. rCDH exhibited values of biochemical parameters similar to those of the natural enzyme, and was able to bind cellulose despite the absence of a carbohydrate-binding module (CBM). Following supplementation of purified rCDH to <I>T. reesei </I>enzymatic cocktail, formation of gluconic acid and increased hemicellulose degradation were observed, thus confirming the previous results observed with <I>P. cinnabarinus </I>secretome.</P><P><B>Conclusions</B></P><P>We demonstrate that CDH offers an attractive tool for saccharification process enhancement due to gluconic acid production from raw lignocellulosic material.</P>