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KMID : 0613820030130010110
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Journal of Life Science
2003 Volume.13 No. 1 p.110 ~ p.117
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Stress Response of a Thermotolerant Alcohol-Fermenting Yeast Strain, Saccharomyces cerevisiae KNU5377, Against Inorganic Acids and Its Alcohol Fermentation Productivity Under the Presence of These Acids
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Yun Hae-Sun
Paik Sang-Kyoo
Kim Il-Sup
Rhee In-Koo
Yu Choon-Bal
Jin Ingn-Yol
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Abstract
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A thermotolerant yeast strain, Saccharomyces cerevisiae KNU5377 (abbreviated as KNU5377), was exposed to inorganic acids including sulfuric, nitric and hydrochloric acid. As a stressor, each inorganic acid is very easily dissociated in water, resulting in lowering environmental pH. When compared with a reference S. cerevisiae ATCC24858, KNU5377 could overcome such a severe condition containing a final 0.4% concentration of sulfuric acid or nitric acid to grow at the overnight culture, but this reference could not. Additionally, this strain showed a surprisingly strong tolerance by surviving despite of exposure to the regime of 0.35% of hydrochloric acid for over 90 min and also to 0.6% of sulfuric
acid for 30 min. On the contrary, both strains could not survive against a final 0.45% concentration of nitric acid. This strain KNU5377 could produce ethanol of 3% in 2 days by using the fermentation medium containing a final 0.3% concentration of sulfuric acid. Moreover, change into a final 0.2% concentration of sulfuric acid caused this strain to enhance fermentation productivity up to about 4.5% even at 40℃. In exposure to a final 0.2% of sulfuric acid for 60 min, trehalose was most accumulated within 30 min in KNU5377, and this suggested a cellular defense system led by this disaccharide was profitable for this strain to lead to no morphological changes.
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KEYWORD
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Inorganic acid, Saccharomyces cerevisiae, Stress response, Alcohol fermentation
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