• Journal of Life Science
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• v.26 no.1
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• pp.17-22
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• 2016

Ethanol is a very valuable material, however, it is also a source of stress, as the accumulation of ethanol in a medium inhibits cell viability and decreases productivity of the target product. Therefore, the ethanol tolerance of yeast, which is closely related to ethanol productivity, is an important factor in industrial ethanol production. In this study, the YDJ1 and PEP5 genes were selected as target genes for elucidating ethanol-tolerant mechanisms by analyzing the expression regulation of these genes. The pA-YDJ1 and pA-PEP5 plasmids containing YDJ1 and PEP5 genes under an ADH1 promoter, respectively, were constructed and transformed into BY4742 (host strain), BY4742△ydj1, and BY4742△pep5 strains. The ethanol tolerance in the BY4742△ydj1/ pA-YDJ1 and BY4742△pep5/pA-PEP5 transformants was restored by overexpression of the YDJ1 and PEP5 genes to the host strain level. The YDJ1 and PEP5 genes were also introduced into the double gene disruptant (BY4742△ydj1△pep5) to investigate the expression regulation of the YDJ1 and PEP5 genes. The simultaneous overexpression of the YDJ1 and PEP5 genes restored ethanol tolerance to the 90% level of the BY4742 strain under 8% ethanol stress. The YDJ1 gene induced more overexpression of the PEP5 gene in the BY4742△ydj1 △pep5/pA-YDJ1, pA-PEP5 strain, suggesting that the YDJ1 gene partially regulates the expression of the PEP5 gene as an upstream regulator.

• Food Science and Preservation
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• v.21 no.5
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• pp.627-635
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• 2014

We investigated the changes in the quality characteristics of Doenjang with low salt contents (6, 8, 10, and 12%) and 10% garlic. The Doenjang was analyzed at an interval of a week during its fermentation for six weeks, at room temperature. Its L color gradually decreased, but its a and b colors did not change significantly. Its salinity increased by about 1% after six weeks. In contrast, immediately after its preparation, its pH was gradually decreased and its acidity was increased for the fermentation. The reducing sugar was significantly increased from 1.34~1.88 g/100 g immediately after its preparation to 7.25~9.13 g/100 g after six weeks, which was higher as the salt concentration decreased. The amino-type nitrogen doubled from 100~130 mg% at 0 week to 210~290 mg% at six weeks, which were lower with the higher salt concentrations. The growth curve of the Bacillus fermentation strains of Doenjang increased to two weeks but gradually decreased since, and the growth of the Bacillus was favorable for up to two weeks in the Doenjang with 10% and 12% salt added. Otherwise, the yeast was reduced rapidly during the early fermentation of the Doenjang, and slightly changed after three weeks of fermentation. The results of this study showed that the reducing sugar and amino-type nitrogen contents of the low-salt garlic Doenjang were higher with the lower salt dose, and the physicochemical quality of the 6%-salt Doenjang was not significantly affected. Thus, we suggest that low-salt Doenjang can be manufactured with the addition of 6% salt and 10% garlic.

• The Korean Journal of Food And Nutrition
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• v.28 no.4
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• pp.666-675
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• 2015

This study was carried out to develop rose sparkling wine with reed root. To make the base wine with reed root extracts, we first blended wild grape wine with reed root extracts (1:9 v/v) and fermented the mixture for 14 days at $20^{\circ}C$. The pH of the control and the rose base wine with reed root extract (RWE) decreased with increasing fermentation time, but acidity showed the opposite behavior. The control and RWE had $7.33^{\circ}Brix$, and $6.90^{\circ}Brix$, respectively at 14 days, with higher sugar content in the control than in RWE. The alcohol content increased as the fermentation progressed and was higher in RWE than in the control at 14.20% and, 13.83%, respectively. Regarding the color, the lightness decreased as the fermentation progressed. The total polyphenol contents of the control and RWE were 29.19 mg/100 mL and, 34.97 mg/100 mL. The flavonoids decreased as the fermentation progressed. The ABTS radical scavenging activity of the control and RWE were 44.26% and, 64.37% while the DPPH radical scavenging activity showed similar results in the control and RWE. In the second test, we added RWE to base wine, because yeast rearing was inhibited at 14% alcohol content. We made sparkling rose wine with 4 strains and fermented the wine for 8 days at $20^{\circ}C$. The pH of the samples decreased with increasing fermentation time, but the acidity showed the opposite behavior. The $^{\circ}Brix$ decreased and the alcohol content increased with increasing fermentation time. The pressure in sample A was $4.30kgf/cm^2$ at 8 days which was the highest in the samples. In the sensory evaluation, the color, flavor, softness and overall acceptability of the control was higher than the other samples. In conclusion, Saccharomyces cerevisiae Vitilevure Quartz was overall the most suitable rose sparkling wine.

• Applied Biological Chemistry
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• v.18 no.1
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• pp.16-22
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• 1975

This experiment was carried out to investigate the physiological characteristics of two original yeasts, 5-Y-5 and 6-Y-6, which selected from 24 Takju yeasts and three mutants, 30-24,30-81 and 40-27. induced from two original yeasts by the irradiation of UV light. The results were summarized as follows. 1) Alcohol tolerances of three mutants were decreased in some degree as compared with those of original yeasts. 2) Tolerances of lactic and citric acids of acid producing mutant 30-81, was increased than those of original yeasts. 3) In the case of using ammonium sulfate as a nitrogen source, two original yeasts and three mutants required Ca-pantothenate as a essential growth factor and four strains of yeasts except the mutant, 30-81, required biotin as a stimulated growth factor, When asparagine was used as a nitrogen source, two original yeasts and three mutants showed the same as above result but the stimulated effect of biotin was far less. 4) Propagation powers of the mutants were weaken than those of original yeasts, particular that of acid producing mutant, 30-81, was the weakest in the three mutants. 5) The optimum temperature for fermentation of original yeasts were $30^{\circ}C\;to\;35^{\circ}C$ but three mutants were $25^{\circ}C\;to\;30^{\circ}C$. 6) The optimum pH for fermentation of original yeasts were pH 5 to 6, and there is no appreciable difference between original yeasts and three mutants. The fermentation power of mutant,30-81, was decreased more rapidly than those of other mutants according to approach neutral. Three mutants were more sensible to heat than original yeasts. 7) Two original yeasts and three mutants were inhibited more over 20 percent of sugar for fermentation and three mutants were more sensible to sugar concentration than original yeasts.