1. College of Materials Engineering Fujian Agriculture and Forestry University Fuzhou 350002 China
2. Department of Biological Systems Engineering University of Wisconsin Madison WI 53706 USA
3. DOE Great Lakes Bioenergy Research Center The Wisconsin Energy Institute University of Wisconsin Madison WI 53726 USA
4. Current address: Department of Chemical Engineering Massachusetts Institute of Technology Cambridge MA 02142 USA
5. Center for Sustainable Catalysis and Engineering K. U. Leuven Kasteelpark Arenberg 23 3001 Heverlee Belgium
6. Department of Biochemistry University of Wisconsin Madison WI 53706 USA