Two neutral thermostable cellulases from Phialophora sp. G5 act synergistically in the hydrolysis of filter paper

Two novel cellulase genes, cbh6A and egGH45, were cloned from Phialophora sp. G5 and successfully expressed in Pichia pastoris. The putative polypeptide of CBH6A consists of a family 1 CBM and a catalytic domain of glycosyl hydrolase family 6 cellobiohydrolases, while deduced EgGH45 only contains a catalytic domain of family 45 endoglucanases. CBH6A and EgGH45 were optimally active at pH 7.0 and 65 °C, and pH 6.0 and 60 °C, respectively. Both enzymes exhibited high activities and stabilities over a wide pH range and had good thermostability at 70 °C. CBH6A and EgGH45 had significant resistance to SDS (10 mM), remaining 35% and 54% activities, respectively. These enzymes had synergic effect on the hydrolysis of filter paper, showing the highest efficiency in the ratio of CBH6A to EgGH45 at 80:20. The properties make this enzyme combination potential for application in textile and detergents industries.