A comparative study of the enzymatic properties of thermostable fungal cellobiohydrolases from the GH family 7

Cellulases are important industrial enzymes, which can be used e.g. in pulp and paper, textile, and detergent industry. Cellulases are also currently being studied and used to convert cellulose containing biomass to ethanol, a transport fuel. The enzymatic degradation of cellulosic biomass to soluble sugars is performed by consortium of enzymes acting in synergy. Despite of the published data available on the kinetic behaviour of various fungal and bacterial cellulases, systematic comparison studies on the enzymatic properties of different cellulases are still lacking. Comparable information would be needed to create a more thorough understanding of the function of these enzymes, and also for the application purposes, e.g. in finding the optimal enzyme mixtures for the total hydrolysis of cellulose. Here, we present results from screening of cellulase producing fungi, and the characterisation of enzymatic properties of the three most interesting thermostable cellobiohydrolases found from the screen. All three cellobiohydrolases belong to the glycosyl hydrolase (GH) family 7, and they were expressed in Trichoderma reesei before the purification and characterisation. Both the catalytic core modules and 2-module forms (composed of the catalytic and the cellulose-binding modules) of the cellobiohydrolases were included in the comparison. The enzymatic properties of these cellobiohydrolases were compared to those of the cellobiohydrolase Cel7A of T. reesei, which is among the most thoroughly studied fungal cellobiohydrolases. Acknowledgements: This study was part of EU-project: Technological improvement for ethanol production from lignocellulose (EU-TIME).