NOVELTY - A variant endoglucanase (EG) or biologically active variant EG fragment is new.    USE - The variant EG and composition are useful for producing at least one fermentable sugar, or a fermentation end product from a biomass substrate. The fermentation product is an alcohol selected from ethanol (preferred) and butanol (all claimed).    DETAILED DESCRIPTION - A variant EG or biologically active variant EG fragment comprises (i) an amino acid sequence comprising at least 70-99% sequence identity to a wild-type EG (SEQ ID NO: 3); and (ii) an amino acid substitution from one or more of the amino acid residues selected from 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 39, 20, 23, 22, 34, 38, 39, 43, 49, 63, 66, 75, 85, 126, 137, 143, 201, 218, 228, 241, 269, 274, 282, 328, 342, 342, 350, 397, 398, 399, 400, 401, 403, 404, 405, 407, 408, 409, 411, 412, 413, 414, 415, 417, 438, 439, 420, 425, 428, 433, 434, 435, 438, 439, 440, 443, 444, 446, 457, and 464, where the residues are numbered with reference to SEQ ID NO: 2. INDEPENDENT CLAIMS are:    (1) a biologically active variant EG fragment of any of SEQ ID NOS: 5, 7 and/or 9;    (2) an enzyme composition comprising the variant EG above;    (3) a polynucleotide comprising a nucleic acid sequence encoding the variant EG above, or a polynucleotide that hybridizes under stringent hybridization conditions to the polynucleotide and/or a complement of a polynucleotide that encodes a polypeptide;    (4) a recombinant nucleic acid construct comprising at least one polynucleotide sequence encoding at least one variant EG, where the polynucleotide is selected from (i) a polynucleotide that encodes a polypeptide comprising an amino acid sequence comprising at least 70-99% identity to SEQ ID NOS: 5, 7 and/or 9, where the amino acid sequence comprises at least one substitution and/or substitution, (ii) a polynucleotide that hybridizes under stringent hybridization conditions to at least a fragment of a polynucleotide that encodes a polypeptide comprising the amino acid sequence of SEQ ID NOS: 1, 4, 6, and/or 8, and where the amino acid sequence comprises at least one substitution and/or at least one substitution, and/or (iii) a polynucleotide that hybridizes under stringent hybridization conditions to the complement of at least a fragment of a polynucleotide that encodes a polypeptide comprising the amino acid sequence of SEQ ID NOS: 1, 4, 6, and/or 8, and where the amino acid sequence comprises at least one substitution and/or at least one substitution;    (5) a recombinant host cell that expresses at least one polynucleotide sequence encoding at least one variant EG above;    (6) a method for producing at least one fermentable sugar from a biomass substrate by contacting the biomass substrate with the enzyme composition of (2), under culture conditions where fermentable sugars are produced;    (7) a method of producing an end product from a biomass substrate by (a) contacting the biomass substrate with a composition of (2), under conditions where at least one fermentable sugar is produced from the biomass substrate; and (b) contacting the fermentable sugar with a microorganism under conditions such that the microorganism uses the fermentable sugar to produce an end-product; and    (8) a method of producing a fermentation end product from a biomass substrate by (a) obtaining at least one fermentable sugar produced according to the method of (6), and (b) contacting the fermentable sugar with a microorganism in a fermentation to produce at least one fermentation end product.