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Efficient cellulolytic enzyme production is important for the development of lignocellulose-degrading enzyme mixtures. However, purification of cellulases from their native hosts is time- and labor-consuming. In this study, a constitutive expression system was developed in Penicillium oxalicum for the secreted production of proteins. Using a constitutive polyubiquitin gene promoter and cultivating with glucose as the sole carbon source, nine cellulolytic enzymes of different origins with relatively high purity were produced within 48 h. When supplemented to a commercial cellulase preparation, cellobiohydrolase I from P. funiculosum and cellobiohydrolase II from Talaromyces verruculosus showed remarkable enhancing effects on the hydrolysis of steam-exploded corn stover. Additionally, a synergistic effect was observed for these two cellobiohydrolases during the hydrolysis. Taken together, the constitutive expression system provides a convenient tool for the production of cellulolytic enzymes, which is expected to be useful in the development of highly efficient lignocellulose-degrading enzyme mixtures.

Efficient cellulolytic enzyme production is important for the development of lignocellulose-degrading enzyme mixtures. However, purification of cellulases from their native hosts is time- and labor-consuming. In this study, a constitutive expression system was developed in

Two major endoglucanase genes (cel7B and cel5A) were cloned from Penicillium decumbens 114-2 using the method of modified thermal asymmetric interlaced polymerase chain reaction (TAIL-PCR). The result of Southern blotting suggested that P. decumbens has a single copy of the cel5A gene and a single copy of cel7B gene in its chromosomal DNA. The expression level of cel5A and cel7B were determined by means of real-time quantitative PCR, suggesting that two genes were coordinately expressed and repressed by glucose and induced by cellulose. Both endoglucanase genes were expressed in Saccharomyces cerevisiae and the recombinant proteins were purified. The recombinant Cel7B and Cel5A were both optimal active at 60 C and pH 4.0. The recombinant Cel7B showed more than 8-fold, 30-fold, 5-fold higher enzyme activity towards carboxymethyl cellulose, barely beta-glucan and PASC respectively in comparison with that of Cel5A. However, their activities toward pNPC and Avicel were minor difference. The result suggested that Cel7B is a strict endoglucanase, while Cel5A show processivity because of its relative higher ability to hydrolyze the crystal cellulose.