An acidic Cel6A, cellobiohydrolase (CBH) II, was purified from Penicillium decumbens and designated as PdCel6A. The deduced internal amino acid sequence of the novel CBH has a high degree of sequence identity with the CBH II from Aspergillus fumigatus. Surprisingly, PdCel6A exhibits characteristics comparable to that of CBH I, as well as CBH II. Similar to CBH I, the novel CBH has a specific activity of 1.9 IU/mg against p-nitrophenyl-beta-D-cellobioside. The enzyme retains about 80% of its maximum activity after 4 h of incubation at pH 2.0. Using delignified corncob residue as the substrate, ethanol concentration increased by 20% during simultaneous saccharification and fermentation when supplemented with low doses of PdCel6A (0.2 mg/g substrate). To our knowledge, this is the first report involving a CBH I-like CBH II. The present paper provides new insight into the role of CBH II in cellulose degradation. (C) 2011 Elsevier Ltd. All rights reserved.