NOVELTY - An isolated polypeptide having cellulolytic enhancing activity is new.    USE - For producing a mutant of a parent cell; in double-stranded inhibitory RNA (dsRNA) molecule comprising siRNA or an miRNA molecule; for producing a protein; for degrading a cellulosic material; and for producing a fermentation product (claimed) fuel e.g. ethanol, n-butanol, isobutanol, biodiesel, jet fuel and platform chemicals e.g. acids, alcohols, ketones, gases, and oils.    ADVANTAGE - The isolated polypeptide has increased efficiency and provides cost- effective enzyme solutions for saccharification of cellulosic material.    DETAILED DESCRIPTION - An isolated polypeptide having cellulolytic enhancing activity, selected from a) a polypeptide having at least 70% sequence identity to the mature polypeptide of (SEQ ID NO: 2) or at least 80% sequence identity to the mature polypeptide of (SEQ ID NO: 4); b) a polypeptide encoded by a polynucleotide that hybridizes under at least very high stringency conditions with the mature polypeptide coding sequence of (SEQ ID NO: 1) or its cDNA sequence, or the mature polypeptide coding sequence of (SEQ ID NO: 3), or its the full-length complement; c) a polypeptide encoded by a polynucleotide having at least 70% sequence identity to the mature polypeptide coding sequence of (SEQ ID NO: 1) or its cDNA sequence, or at least 80% sequence identity to the mature polypeptide coding sequence of (SEQ ID NO: 3); d) a variant of the mature polypeptide of (SEQ ID NO: 2) or the mature polypeptide of (SEQ ID NO: 4) (all as available on WIPO website. Sequences not defined here may be found at ftp://ftp.wipo.net/pub/published pct sequences/publication) comprising a substitution, deletion, and/or insertion at least one position; and e) a fragment of the polypeptide of (a), (b), (c), or (d) that has cellulolytic enhancing activity. INDEPENDENT CLAIMS are included for the following:    (1) new isolated polypeptide comprising a catalytic domain selected from a') a catalytic domain having at least 80% sequence identity to amino acids 24-242 of (SEQ ID NO: 4); b') a catalytic domain encoded by a polynucleotide that hybridizes under at least very high stringency conditions with nucleotides 70-726 of (SEQ ID NO: 3), or its full-length complement; c') a catalytic domain encoded by a polynucleotide having at least 80% sequence identity to nucleotides 70-726 of (SEQ ID NO: 3); d') a variant of amino acids 24-242 of (SEQ ID NO: 4) comprising a substitution, deletion, and/or insertion at least one position; and e') a fragment of the catalytic domain of (a'), (b'), (c'), or (d') that has cellulolytic enhancing activity;    (2) new isolated polypeptide comprising a carbohydrate binding domain operably linked to a catalytic domain, where the binding domain is selected from a'') a carbohydrate binding domain having at least 80% sequence identity to amino acids 326-366 of (SEQ ID NO: 4); b'') a carbohydrate binding domain encoded by a polynucleotide that hybridizes under at least very high stringency conditions with nucleotides 976-1098 of (SEQ ID NO: 3) or its full-length complement; c'') a carbohydrate binding domain encoded by a polynucleotide having at least 80% sequence identity to nucleotides 976-1098 of (SEQ ID NO: 3); d'') a variant of amino acids 326-366 of (SEQ ID NO: 4) comprising a substitution, deletion, and/or insertion at least one position; and e'') a fragment of the carbohydrate binding domain of (a''), (b''), (c''), or (d'') that has binding activity;    (3) a composition comprising the polypeptide;    (4) new isolated polynucleotide encoding the polypeptide;    (5) new recombinant host cell comprising the polynucleotide operably linked to at least one control sequence that direct the production of the polypeptide;    (6) producing the polypeptide;    (7) a transgenic plant, plant part or plant cell transformed with a polynucleotide encoding the polypeptide;    (8) producing a mutant of a parent cell, involving inactivating a polynucleotide encoding the polypeptide, which results in the mutant producing less of the polypeptide than the parent cell;    (9) new double-stranded inhibitory RNA (dsRNA) molecule comprising a subsequence of the polynucleotide, where optionally the dsRNA is an siRNA or an miRNA molecule;    (10) producing a protein, involving cultivating a recombinant host cell comprising a gene encoding a protein operably linked to the polynucleotide, where the gene is foreign to the polynucleotide encoding the signal peptide, under conditions conducive for production of the protein;    (11) degrading a cellulosic material, involving treating the cellulosic material with an enzyme composition in the presence of the polypeptide having cellulolytic enhancing activity;    (12) producing a fermentation product, involving saccharifying a cellulosic material with an enzyme composition in the presence of the polypeptide having cellulolytic enhancing activity; fermenting the saccharified cellulosic material with fermenting microorganisms to produce the fermentation product; and recovering the fermentation product from the fermentation; and    (13) a whole broth formulation or cell culture composition comprising the polypeptide.