Background: A higher-salt-tolerant mutant strain Zygosaccharomyces rouxii 3-2 (strain S3-2) that could be used for improving the flavour of high-salt liquid state soy sauce was previously constructed from parent strain Z. rouxii (strain S) by genome shuffling. However, whether the mutations in this strain affect HOG1 encoding MAPK Hog1p and improve intracellular glycerol production remains to be elucidated.
Results: Although two mutations in the ORF and one in the promoter of the HOG1 gene sequence of strain S3-2 occurred compared with that of strain S, there was no significant difference in secondary and tertiary structures between S3-2Hog1p and SHog1p. It was found that the expression level of S3-2HOG1 was higher than that of SHOG1 in YPDN medium with high salt concentration. Furthermore, overexpression of S3-2HOG1 in Saccharomyces cerevisiae W303-1A could improve the salt tolerance and osmotolerance of engineered yeast compared with that of SHOG1.
Conclusion: Enhancement of the transcription level of HOG1 induced by mutation in the promoter region may be one of the main reasons for the improved salt tolerance of strain S3-2 compared with that of strain S. Considering food security, the conservation of S3-2HOG1 would be beneficial for application of strain S3-2 in the fermentation of soy sauce.
Keywords: HOG1; Zygosaccharomyces rouxii mutant strain; osmostress; salt tolerance.
© 2013 Society of Chemical Industry.