7-42: Lignin-derived inhibition of GH7 cellobiohydrolases – insight to the inhibitory mechanism

Enzymatic hydrolysis of lignocellulosic biomass is restricted due to the presence of lignin in the pretreated raw materials. Insoluble lignin is thought to interfere the cellulose hydrolysis by adsorbing hydrolytic enzymes and by shielding cellulosic surfaces from an enzymatic attack. Enzyme binding on lignin is shown to inactivate the major components of the Trichoderma reesei cellulases as well as to prevent enzyme recycling. Therefore, in-depth understanding of the binding phenomenon could benefit enzyme and process development. In this study, isolated lignin preparations from steam pretreated spruce and hydrothermally pretreated wheat straw were employed to study the binding of GH7 cellobiohydrolases on lignin and the inhibitory effect of lignin during cellulose (Avicel) hydrolysis. In the hydrolysis, high temperature enhanced the negative effect of lignin. Furthermore, increase in temperature promoted the formation of stronger enzyme-lignin interactions in adsorption studies. The paper will discuss these findings in relation to the inhibition mechanism.  

Support for this work was provided by EU-project NEMO, Novel high performance enzymes and micro-organisms for conversion of lignocellulosic biomass to bioethanol, Grant no. 222699, (http://nemo.vtt.fi) and the Graduate School for Biomass Refining (Academy of Finland).