Heterologous expression of <it>Pycnoporus cinnabarinus </it>cellobiose dehydrogenase in <it>Pichia pastoris </it>and involvement in saccharification processes

<p>Abstract</p> <p>Background</p> <p>Cellobiose dehydrogenase (CDH) is an extracellular hemoflavoenzyme produced by lignocellulose-degrading fungi including <it>Pycnoporus cinnabarinus</it>. We investigated the cellulolytic system of <it>P. cinnabarinus</it>, focusing on the involvement of CDH in the deconstruction of lignocellulosic biomass.</p> <p>Results</p> <p>First, <it>P. cinnabarinus </it>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 <it>P. cinnabarinus </it>secretome in saccharification processes, the <it>Trichoderma reesei </it>enzymatic cocktail was supplemented with the <it>P. cinnabarinus </it>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. <it>P. cinnabarinus </it>CDH was heterologously expressed in <it>Pichia pastoris </it>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 <it>T. reesei </it>enzymatic cocktail, formation of gluconic acid and increased hemicellulose degradation were observed, thus confirming the previous results observed with <it>P. cinnabarinus </it>secretome.</p> <p>Conclusions</p> <p>We demonstrate that CDH offers an attractive tool for saccharification process enhancement due to gluconic acid production from raw lignocellulosic material.</p>

Abstract licence: CC BY-NC-ND

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