1. Antibiotics Laboratory, The Institute of Physical and Chemical Research (RIKEN), Hirosawa 2-1, Wako-shi, Saitama 351-01, Japan, Department of Engineering, Toyo University, Nakanodai 2100, Kujirai, Kawagoe, Saitama 350, Japan, and Research Institute of Life Science, Snow Brand Milk Products Co., Ltd., Ishibashi-machi, Shimotsuga-gun, Tochigi 329-05, Japan