1. Samyang Genex Biotech Research Institute, 63-2 Hwaam-Dong, Yusung-Gu, Taejeon 305-348, Korea; Department of Food Science and Technology and Research Center for New Bio-Materials in Agriculture, College of Agriculture and Life Sciences, Seoul National University, Suwon 441-744, Korea; and Department of Biology, University of Incheon, Incheon 402-749, Korea