TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Sequences: The isolated polypeptide comprises an amino acid sequence that has at least 80-90% identity to SEQ ID NO: 135. The isolated polypeptide comprises the N-terminal sequence derived from the first beta -glucosidase and the C-terminal sequence derived from the second beta -glucosidase, where the first beta -glucosidase and the second beta -glucosidase are different from each other. The N-terminal sequence and the C-terminal sequences are not directly connected, but are functionally connected via a linker domain, where the N-terminal sequence, the C-terminal sequence, or the linker domain comprises a loop region sequence of 3-11 amino acid residues in length, comprising an amino acid sequence of SEQ ID NO: 171 or 172. The isolated polypeptide has improved stability as compared to the first beta -glucosidase or to the second beta -glucosidase, where the improved stability is an increased resistance to proteolytic cleavage under storage conditions or production conditions. The N-terminal sequence comprises an amino acid sequence that has at least 90% sequence identity to a sequence of the same length of SEQ ID NO: 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 79, where the C-terminal sequence comprises a sequence motif of SEQ ID NO: 170. The N-terminal sequence comprises one or more or all of sequence motifs SEQ ID NOs: 164-169, and the C-terminal sequence comprises an amino acid sequence that has at least 90% sequence identity to a sequence of the same length of SEQ ID NO: 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78 or 79. The N-terminal sequence follows 3 or more, 4 or more, 5 or more of sequence motifs SEQ ID NOs: 136-148, and where the C-terminal sequence follows 2 or more, 3 or more, or 4 or more of sequence motifs SEQ ID NOs: 149-156. The isolated polynucleotide comprises a nucleotide sequence having at least 90% identity to SEQ ID NO: 83. Sequences not defined here may be found at ftp://ftp.wipo.int/pub/published_pct_sequences/publication. Preferred Composition: The composition further comprises one or more cellulases selected from endoglucanases, GH61/endoglucanases, cellobiohydrolases and other beta-glucosidases. The composition further comprises one or more hemicellulases selected from xylanases, beta -xylosidases, or L- alpha -arabinofuranosidases. The beta -glucosidase is present in 1-75 wt.%, relative to the total amount of proteins in the composition. The composition is a culture mixture or a fermentation broth, where the composition is a whole broth formulation. Preferred Host Cell: The recombinant host cell is a bacterial or fungal cell. The recombinant host cell is selected from a Bacillus or an Escherichia coli. The recombinant host cell is selected from a Trichoderma, Aspergillus, Chrysosporium, or yeast cell. Preferred Method: In the method of hydrolyzing a cellulosic biomass material, the biomass material is subjected to pretreatment, where the pretreatment comprises an acidic pretreatment or a basic pretreatment, or a combination of an acidic pretreatment and a basic pretreatment. EXAMPLE - No suitable example given.