1. Life Science Division, Korea Institute of Science and Technology, P.O. Box 131, Cheongryang, Seoul 130-650, South Korea, Department of Biotechnology, Yonsei University 220, Sinchon-dong, Seodaemun-gu, Seoul 120-749, South Korea, and Korea Research Institute of Chemical Technology, P.O. Box 107, Yusung-gu, Taejeon 305-343, South Korea