1. 원유와 시유 40점에서 내열성균으로 생각되는 330균주의 세균이 분리되었다. 2. 현미경적 관찰, 생리적시험, 단백질분해성과 지방분해성으로 보아 Bacillus stearothermophilus 125균주, Bacillus coagulans 69균주, Bacillus subtilis 57균주, Bacillus cereus 76균주, Lactobacillus thermophilus 3균주로 동정되었다. 3. 이들 반이상의 균주들은 skim milk배지에서 $85^{circ}C$, 15분간 처리에도 생존할 수 있었다.
1. Three hundred and thirty three strains of thermoduric bacteria from raw milk, H.T.S.T. sterilized milk and U.H.T. sterilized milk in the market were isolated after heat treatment at $65^{circ}C$ for 30 minutes. 2. By microscopical and physiological examination, including the tests for proteolysis and lipolysis, the isolates were identified as 125 strains of Bacillus stearothermophilus, 69 strains as Bacillus coagulans, 57 strains as Bacillus subtilis, 76 strains as Bacillus cereus and 3 strains as Lactobacillus thermophilus. 3. The susceptibility of the selected thermoduric strains to heat, the vegetative cells of some strains in skim milk survived the heat treatment at $65^{circ}C$ for 30 minutes or $85^{circ}C$ for 20 minutes but not survived at $100^{circ}C$ for 10 minutes.
