1. Central Research Institutes, Taiyo Kagaku Co., Yokkaichi, Mie, 510, Japan
2. Frontier Research Program, Laboratory for Intestinal Flora, Riken, Wako, Saitama, 351-01, Japan
3. Faculty of Agriculture, The University of Tokyo, Tokyo, 113, Japan
4. The Institute of Physical & Chemical Research, Wako, Saitama, 351-01, Japan