Clostridium cellulovorans degrades cellulose efficiently to small oligosaccharides, which are used as an energy source. To characterize enzymes related to degrading small oligosaccharides, a gene was cloned for an extracellular non-cellulosomal beta-glucan glucohydrolase (Bg1A) classified as a family-1 glycosyl hydrolase in C cellulovorans. Recombinant Bg1A (rBg1A) had higher activity on long glucooligomers than on cellobiose. When cellulosomes and rBg1A were incubated with cellulose, the oligosaccharides produced were degraded more effectively to cellobiose and glucose, than with cellulosomes alone, indicating that Bg1A facilitated the degradation of accessible cello-oligo saccharides produced from cellulose by C cellulovorans cellulosomes. Thus, this is an example of an extracellular non-cellulosomal enzyme working in a cooperative manner with cellulosomes to degrade cellulose to sugars. (c) 2006 Elsevier Inc. All rights reserved.