1. Department of Biomedical Food Research, National Institute of Infectious Diseases, Shinjuku-ku, Tokyo 162-8640,1
2. Department of Food and Nutrition, Tokai University Junior College, Shizuoka 420-8511,2 Tokyo
3. Kenbikyoin Foundation, Chuo-ku, Tokyo 103-0015,3
4. Division of Microbiology, National Institute of Health Sciences, Setagaya-ku, Tokyo 158-8501,4and
5. The University of Tokyo, Graduate School of Agricultural and Life Sciences, Bunkyo-ku, Tokyo 113-8657,5 Japan