1. Department of Biological Resource Sciences, Akita Prefectural University, Nakano Shimoshinjyo, Akita 010-0195, Japan.
2. Corresponding author. Phone: +81-18-872-1584. Fax: +81-18-872-1676. E-mail: hashizume@akita-pu.ac.jp
3. National Research Institute of Brewing, Kagamiyama, Higashi-hiroshima 739-0046, Japan.