TECHNOLOGY FOCUS - BIOLOGY - Preferred Components: The fermenting microorganism is bacterium or yeast. The bacterium is selected from Zymomonas mobilis, Escherichia coli and Klebsiella oxytoca. The yeast is selected from Saccharomyces cerevisiae, Saccharomyces uvarum, Kluyveromyces fragilis, Kluyveromyces lactis, Candida pseudotropicalis, and Pachysolen tannophilus. Preferred Cell: The recombinant cell (L1) is a eukaryotic cell or a filamentous fungal cell, where the filamentous fungal cell is of the genus Aspergillus, Penicillium, Rhizopus, Chrysosporium, Myceliophthora, Trichoderma, Humicola, Acremonium or Fusarium (preferably Aspergillus niger, Aspergillus oryzae, Trichoderma reesei, Penicillium chrysogenum, Myceliophthora thermophila, or Rhizopus oryzae. The recombinant cell (L1) is a yeast cell of the genus Saccharomyces, Kluyveromyces, Candida, Pichia, Schizosaccharomyces, Hansenula, Klockera, Schwanniomyces or Yarrowia (preferably the species of Saccharomyces cerevisiae, Saccharomyces bulderi, Saccharomyces barnetti, Saccharomyces exiguus, Saccharomyces uvarum, Saccharomyces diastaticus, Kluyveromyces lactis, Kluyveromyces marxianus or Kluyveromyces fragilis). The recombinant cell (L1) is Saccharomyces cerevisiae cell. The host cell (L2) is a prokaryotic cell, a bacterial cell, or a eukaryotic cell.    TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preparation (claimed): Preparation of the polypeptide (D1) involves culturing the recombinant cell engineered to express the polypeptide under conditions in which the polypeptide is expressed, where the polypeptide comprises a signal sequence and the recombinant cell is cultured under conditions in which the polypeptide is secreted from the recombinant cell; and further involves recovering the polypeptide from the cell culture. In the method, the step of recovering the polypeptide involves centrifuging away cells and/or cellular debris; and filtering away cells and/or cellular debris. Preferred Polypeptide: The polypeptide (D1) and (D2) further comprises a signal sequence. The polypeptide (D1) comprises Arg268 substitution and Arg411 substitution, where the Arg268 substituent and Arg411 substituent is lysine or alanine. In the polypeptide (D1), the variant CBH I catalytic domain comprises an amino acid sequence having at least 90 (preferably at least 95)% sequence identity to amino acids 18-444 of SEQ ID NO: 2, where, other than Arg268 and/or Arg411 substitutions, the variant CBH I catalytic domain comprises the sequence of amino acids 18-444 of SEQ ID NO: 2. The variant CBH I catalytic domain comprises one of the following amino acid substitutions or pairs of amino acid substitution as compared to a protein of SEQ ID NO: 2: Arg-268-Lys and Arg-411-Lys; Arg-268-Lys and Arg-411-Ala; Arg-268-Ala and Arg-411-Lys; Arg-268-Ala and Arg-411-Ala; Arg-268-Ala; Arg-268-Lys; Arg-411-Ala; and Arg-411-Lys. The variant CBH I catalytic domain does not comprise Arg-268-Ala substitution. The polypeptide (D1) does not comprise amino acid sequence of amino acid sequence containing 497 amino acids (SEQ ID NO: 150) and containing 497 amino acids (SEQ ID NO: 151), containing 529 amino acids (SEQ ID NO: 152) or containing 504 amino acids (SEQ ID NO: 153), as given in the specifications. The variant CBH I catalytic domain does not comprise Arg-411-Ala substitution. The variant CBH I catalytic domain comprises an amino acid sequence having at least 90 (preferably at least 95)% sequence identity to amino acids 26-455 of amino acid sequence containing 529 amino acids (SEQ ID NO: 1), as given in the specification, where, other than Arg268 and/or Arg411 substitutions, the variant CBH I catalytic domain comprises the sequence of amino acids 26-455 of SEQ ID NO: 1. The variant CBH I catalytic domain comprises one of the following amino acid substitutions or pairs of amino acid substitutions as compared to a protein of SEQ ID NO: 1: Arg-273-lys and Arg-422-Lys; Arg-273-Lys and Arg-422-Ala; Arg-273-Ala and Arg-422-Lys; Arg-273-Ala and Arg-422-Ala; Arg-273-Ala; Arg-273-Lys; Arg-422-Ala; and Arg-422-Lys. The variant CBH I catalytic domain comprises the amino acid substitutions Arg-273-Lys and Arg-422-Lys as compared to a protein of SEQ ID NO: 1. The variant CBH I catalytic domain does not comprise both Arg-273-Lys and Arg-422-Lys substitutions as compared to a protein of SEQ ID NO: 1. The variant CBH I catalytic domain comprises an amino acid sequence having at least 90% or at least 95% sequence identity of the amino acid sequence of the catalytic domain of an amino acid sequence including SEQ ID NO: 1 to SEQ ID NO: 149, all are as given in the specifications, for e.g. amino acid sequence containing 526 amino acids (SEQ ID NO: 5), containing 539 amino acids (SEQ ID NO: 8), containing 456 amino acids (SEQ ID NO: 9), containing 419 amino acids (SEQ ID NO: 21), or containing 450 amino acids (SEQ ID NO: 25), as given in the specifications. The variant CBH I catalytic domain is operably linked to a cellulose binding domain. The catalytic domain is operably linked to a cellulose binding domain via a linker. The cellulose binding domain is C/N-terminal to the catalytic domain. The polypeptide (D1) and (D2) are a mature polypeptide. In the polypeptide (D2), amino acid sequence has at least 97% sequence identity to the amino acid sequence corresponding to positions 18-444 of SEQ ID NO: 2. Preferred Composition: The composition (C1) comprises the polypeptide (D1) and (D2) (at least 1, preferably at least 5, especially at least 25)%. The composition is a whole cellulase or filamentous fungal whole cellulase, where the whole cellulase is produced by a host cell that recombinantly expresses polypeptide. Preferred Broth: The fermentation broth (C2) is a filamentous fungal fermentation broth or a cell-free fermentation broth. Preferred Method: The method (M1) further involves recovering monosaccharides. The method (M2) further involves, prior to step (a), pretreating the biomass. In the method (M3) and (M4), the modification is by site directed mutagenesis. Preferred Vector: The vector (V1) further comprises an origin of replication; and a promoter sequence operably linked to the nucleotide sequence. In the vector (V1), the promoter sequence is operable in yeast or filamentous fungi. EXAMPLE - No suitable example given.