A temperature-sensitive osmophilic mutant of Zygosaccharomyces rouxii,
OS15, was isolated, which required high salt or sugar concentration f
or growth above 30 degrees C. Cell viability at 35 degrees C in the pr
esence of NaCI was higher than in the absence of NaCI, and a survival
ratio of the mutant cells after incubation at 55 degrees C was also hi
gher in the presence of NaCI than NaCI-free condition. Furthermore, re
sistance to UV light, hygromycin B and. geneticin was improved in the
presence of NaCI. There was no difference between the patent and the m
utant in fatty acid saturation and microscopic cell shape under NaCI c
ondition.