1. Advanced Chemical Technology Division, Korea Research Institute of Chemical Technology, P.O. Box 107, Yuseong, Daejeon 305-600, Korea
2. Key Laboratory of Coal Science and Technology (Taiyuan University of Technology), Ministry of Education and Shanxi Province, Taiyuan 030024, Shanxi, China
3. Department of Biological and Chemical Engineering, Gunma University, Kiryu 376-8515, Japan