The efficient degradation of natural lignocellulose or microcrystalline cellulose needs balanced cellulase system. Many cellulase systems secreted by filamentous fungi are not optimized for cellulose hydrolysis due to lack of one or more enzyme components. Generally, beta-glucosidase is a rate limiting enzymein cellulolytic enzyme systems secreted by most filamentous fungi. Here, we report a new screening strain Penicillium documben peni-1, who can secrete high beta-glucosidase (6 U/mL) on high carbon source culture, in addition, more high yield strains (10-15 U/mL) of beta-glucosidase are achieved by its overexpression with three strong constitutive promoters (rodA, ubiA PGML) that were screened from Penicillium oxalicum 114-2. The results are further partially confirmed on the strain 114-2D15A, a strain that was obtained by deletion of the major amylase amy15A and secreted few extracellular proteins on starch. Our results demonstrated that 114-2D15A is a new homologous expression host for the characterization research of CAZy family proteins of filamentous fungi on starch with those optional strong promoters. Furthermore, it also gives a more convenient way to study the better composition of cellulase enzyme-corresponding different substrates on cellulose.
Keywords: Beta-glucosidase; Cellulase; Strong promoter; Homologous expression; Penicillium oxalicum.