Three approaches for enrichment of Penicillium verruculosum cellulose multienzyme cocktails with a heterologously expressed Aspergillus niger beta-glucosidase (AnBGL) for boosting the hydrolytic performance of cellulases were tested. The best boosting effects (73-113%) on glucose yield in 72-h hydrolysis of milled aspen wood and Avicel provided the enzyme preparation obtained by cofermentation of two P. verruculosum strains, one of which was a basic high-cellulase strain, while the other was capable to produce the heterologously expressed AnBGL (up to 80% of the total protein when used in a separate fermentation). Two other approaches, based on individual fermentations of P. verruculosum strains, carrying the heterologous AnBGL under the control of either a strong cbh1 gene promoter or a weaker hist4 gene promoter, also provided notable boosting effects, although they were less pronounced than in the first mentioned case. (C) 2015 Elsevier Ltd. All rights reserved.