Poster Presentation 1B-24

Quantitative Comparison of the Inhibition of Cellulolytic Enzymes by Lignin and Classical Cellulase Inhibitors

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

Maobing Tu, Dan Xie, Douglas Kilburn and Jack Saddler

Forest Products Biotechnology Group

Department of Wood Science

2424 Main Mall

University of British Columbia

Vancouver, B.C. Canada V6T 1Z4

Phone: (1-604) 822-5936

Fax: (1-604) 822-9159

E-mail: alberlin@interchange.ubc.ca

Bioconversion of lignocellulosic fiber to ethanol is a promising technology for production of renewable transportation fuel. However, processing costs, particularly the cost of pretreatment and subsequent enzymatic hydrolysis, continue to impede full-scale commercialization on a level comparable to starch-based technologies. The amount, distribution and chemical reactivity of lignin on the fiber surface, and the interaction of lignin with cellulolytic enzymes, have been identified as primary factors affecting enzyme accesibility and catalytic efficiency. Qualitative data indicates that lignin is a strong inhibitor of cellulases but no quantitative analysis of enzyme inhibition by lignin has yet been reported. As part of a systematic study to evaluate the impact of lignin on hydrolysis, we have quantified inhibition of a Trichoderma reesei cellulase complex and a β-glucosidase from Aspergillus niger by classical cellulase inhibitors and various lignin preparations. The data show that inhibition by lignin, on a mass basis, is comparable to inhibitors such as δ-gluconolactone and glucose. Furthermore, while δ-gluconolactone and glucose inhibition is competitive, inhibition by lignin appears mixed.