b) Upper temperature limit test Selected strains were tested to determine the upper temperature limit for fermen- tation. A fresh culture grown at 37℃ was inoculated into 5 mL of YPD screening medium in a test tube containing a Durham tube. The test tubes were incubated in three Bio Shaker BR-15LF incubators (Taitec Co. Ltd., Tokyo, Japan) with gentle shaking twice a day. The incubators were kept at a constant temperature, and each was increased in intervals of 1℃ per day. The accumulation of gas in the Durham tube was observed daily. The upper temperature limit for fer- mentation was considered to be located between the lowest temperature at which no fermentation occurred after 5 days and the next lowest temperature at which fermentation had occurred as described by Walt and Yarrow (1984).