Poster Presentation 1B-07

Weak Lignin-Binding Enzymes – A Novel Approach to Improve the Activity of Cellulases for Hydrolysis of Lignocellulosics

Alex Berlin,* Neil Gilkes, Arwa Kurabi, David Gregg, Renata Bura, Sarah Leung,

Maobing Tu, Dan Xie, Douglas Kilburn and Jack Saddler

Forest Products Biotechnology Group

Department of Wood Science

University of British Columbia, Vancouver, Canada

2424 Main Mall, Vancouver, B.C. Canada  V6T 1Z4

Phone: (1-604) 822-5936

Fax: (1-604) 822-9159

E-Mail: alberlin@interchange.ubc.ca

Economic barriers preventing commercialization of lignocellulose-to-ethanol bioconversion processes include the high cost of hydrolytic enzymes. One route to cost reduction is to improve the activities of cellulases by genetic manipulation. However improvement is usually determined using “ideal” cellulosic substrates and results are not necessarily applicable to more realistic substrates such as hardwood and softwood lignocellulosics. For these substrates, non-productive binding or inactivation of enzymes by the lignin component are important factors limiting catalytic efficiency. A better understanding of these factors could allow engineering of enzymes with superior performance on lignocellulose. To prove this concept, we have shown that some naturally-occurring cellulases have a low affinity for lignin but similar catalytic activity on model cellulosic substrates. Moreover, although cellulose-binding domains are hydrophobic and probably participate in lignin binding, we show that cellulases lacking this domain still have a high affinity for lignin indicating the presence of lignin binding sites on the catalytic domain.