NOVELTY - A polypeptide comprising either a variant cellobiohydrolase II (CBH II) catalytic domain (CD), variant (CBH II) cellulose binding domain (CBD), variant (CBH II) (CBD-CD) linker sequence, or variant (CBH II) catalytic domain having specific substitutions is new.    USE - For saccharifying biomass or for producing fermentation product (all claimed); in variety of agricultural and industrial applications; in conversion of cellulose into fermentable sugars and for related fields of cellulosic material processing such as pulp and paper, textiles and animal feeds.    ADVANTAGE - The polypeptide comprises cellobiohyrolases with improved specific activity. The variant CBH II polypeptides engineered to include amino acid substitutions that increase specific activity as compared to a wild-type CBH II. The variant CBH II polypeptides comprising the amino acid substitution that result in increased specific activity.    DETAILED DESCRIPTION - A polypeptide comprising either a variant cellobiohydrolase II (CBH II) catalytic domain, where the catalytic domain has at least one amino acid substitutions selected from: Ile235Val substitution; Ser104Val substitution; Lys309His substitution; Ser115Ala substitution; and Ser115Met substitution; variant (CBH II) cellulose binding domain, where the cellulose binding domain has at least one amino acid substitutions selected from: Gly37Ser substitution; and Ala33Lys substitution; a variant (CBH II) single sequence (SS) linker sequence, where the SS linker sequence has at least one amino acid substitutions selected from Ler21Arg substitution; Glu23Lys substitution; and an Glu23Asn substitution; variant (CBH II) CBD-CD linker sequence, where the CBD-CD linker sequence has at least one amino acid substitutions selected from: Pro64Trp substitution; Pro64Glu substitution; Gly65Leu substitution; Glu66Arg substitution; and Gly67Lys substitution; or variant (CBH II) catalytic domain, where the catalytic domain has at least one substitutions selected from: Asp194Asn substitution, an Ala200Leu substitution, Ser421Cys substitution, Asp426Asn substitution, Ala429Ser substitution, Thr430Pro substitution, Trp434Ala substitution, Ala438Leu substitution, Ser439Pro substitution, Ala440Asp substitution, Leu442Thr substitution, Gln443Pro substitution, and Pro444Asn substitution is new. INDEPENDENT CLAIMS are included for the following:    (1) a composition comprising the polypeptide;    (2) a fermentation broth comprising the polypeptide;    (3) saccharifying (M1) biomass involving: treating biomass with the composition or with the fermentation broth;    (4) producing (M2) a fermentation product involving: treating biomass with the composition or with the fermentation broth, thus producing fermentable sugars; and culturing a fermenting microorganism in the presence of the fermentable sugars produced in first step under fermentation conditions, thus producing a fermentation product;    (5) a nucleic acid comprising a nucleotide sequence encoding the polypeptide;    (6) a vector comprising the nucleic acid;    (7) a recombinant cell engineered to express the nucleic acid;    (8) a host cell transformed with the vector;    (9) producing (M3) the polypeptide;    (10) generating (M4) a nucleic acid that encodes a variant CBH II polypeptide having increased specific activity as compared to a reference CBH II polypeptide involving: modifying the nucleotide sequence of a CBH II-encoding nucleic acid so that the nucleic acid encodes a variant CBH II polypeptide, where the variant CBH II polypeptide comprises: Ile235Val substitution; Pro64Trp substitution; Pro64Glu substitution; Leu21Arg substitution; Ser104Val substitution; Gly37Ser substitution; Gly65Leu substitution; Lys309His substitution; Glu66Arg substitution; Ser115Ala substitution; Gly67Lys substitution; Glu23Lys substitution; Ser115Met substitution; Ala33Lys substitution; or Glu23Asn substitution, thus generates nucleic acid that encodes a CBH II polypeptide having increased specific activity as compared to a reference CBH II polypeptide; and    (11) generating (M5) a nucleic acid that encodes a variant CBH II polypeptide having increased specific activity as compared to a reference CBH II polypeptide involving: modifying the nucleotide sequence of a CBH II-encoding nucleic acid so that the nucleic acid encodes a variant CBH II polypeptide, where the variant CBH II polypeptide comprises: Asp194Asn substitution; Ala200Leu substitution; Ser421Cys substitution; Asp426Asn substitution; Ala429Ser substitution; Thr430Pro substitution; Tyr434Ala substitution; Ala438Leu substitution; Ser439Pro substitution; Ala440Asp substitution; Leu442Thr substitution; Gln443Pro substitution; and Pro444Asn substitution, thus generating a nucleic acid that encodes a CBH II polypeptide having increased specific activity as compared to a reference CBH II polypeptide.