• Journal of Microbiology and Biotechnology
• /
• v.30 no.12
• /
• pp.1876-1884
• /
• 2020

Ethanol often accumulates during the process of wine fermentation, and mitophagy has critical role in ethanol output. However, the relationship between mitophagy and ethanol stress is still unclear. In this study, the expression of ATG11 and ATG32 genes exposed to ethanol stress was accessed by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). The result indicated that ethanol stress induced expression of the ATG11 and ATG32 genes. The colony sizes and the alcohol yield of atg11 and atg32 were also smaller and lower than those of wild type strain under ethanol whereas the mortality of mutants is higher. Furthermore, compared with wild type, the membrane integrity and the mitochondrial membrane potential of atg11 and atg32 exhibited greater damage following ethanol stress. In addition, a greater proportion of mutant cells were arrested at the G1/G0 cell cycle. There was more aggregation of peroxide hydrogen (H2O2) and superoxide anion (O2•-) in mutants. These changes in H2O2 and O2•- in yeasts were altered by reductants or inhibitors of scavenging enzyme by means of regulating the expression of ATG11 and ATG32 genes. Inhibitors of the mitochondrial electron transport chain (mtETC) also increased production of H2O2 and O2•- by enhancing expression of the ATG11 and ATG32 genes. Further results showed that activator or inhibitor of autophagy also activated or inhibited mitophagy by altering production of H2O2 and O2•. Therefore, ethanol stress induces mitophagy which improves yeast the tolerance to ethanol and the level of mitophagy during ethanol stress is regulated by ROS derived from mtETC.

• The Korean Journal of Food And Nutrition
• /
• v.37 no.2
• /
• pp.57-66
• /
• 2024

The objective of this study was to investigate the quality characteristics of Campbell Early grape-added traditional Korean wines (yakju) prepared with different yeasts and pretreatments. The first pretreatment (A) was prepared by crushing the grapes, the second method (B) was prepared by heating the grapes at 60~70℃ for 30 minutes, and the third method (C) was prepared by freeze-concentrating grape juice. The pH of the fermented wines ranged from 3.77 to 4.10, and the total acidity of the samples ranged from 0.32 to 0.62%. The a value (redness) ranged from -0.40 to 17.89, which was higher in Campbell Early-added samples than in the controls (grapes not added). Total polyphenol content was the highest in samples prepared by crushing or heating Campbell Early grapes with ES22, and the total flavonoid contents were the highest in samples prepared by crushing Campbell Early grapes with ES22. The anthocyanin contents were also the highest in the samples fermented by heating Campbell Early grapes. ABTS and DPPH radical scavenging activities were also the highest (84.08 and 77.56%, respectively) in samples fermented by heating Campbell Early grapes.

• Food Science and Preservation
• /
• v.18 no.4
• /
• pp.604-611
• /
• 2011

Several wild yeasts were isolated from Korean grape varieties before and during spontaneous fermentation. Among them, four strains were isolated based on the alcohol content and flavor production in wine after fermentation of apple juice. In this study, the four yeast strains were identified and characterized. PCR-restriction fragment length polymorphism analysis of ITS I-5.8S-ITS II region with restriction endonuclease Hae III and Hinf I resulted in that all the strains showed a typical pattern of Saccharomyces cerevisiae. Pulse field gel electrophoresis showed three different chromosome patterns with a same band between strains SS89 and SS812. When ITS I-5.8S-ITS II sequences of the four strains were compared with one another, they were similar to those of Saccharomyces cerevisiae CBS 4054 type strain. Identity of the sequences was higher than 97% with those of the type strain. Phylogenetic analysis showed based on the sequences showed they were genetically closed to the type strain. The four identified strains were tested in a medium containing 200 ppm potassium metabisulfite, and the MM10 and WW108 inhibition rates resulted at up to 24 h. The four strains were tested at an incubation temperature of $30^{\circ}C$. The 30% sugar concentration in the medium (w/v) showed the highest growth in 36 h, especially in the case of SS89, which was close to growth 40. The four strains were tested in an 8% ethanol medium (v/v). Alcohol tolerance was initially kept in the incubation process. The strains began to adapt, however, to the exceeded resistance. The four strains showed the lowest inhibition rate at 24 h.

• The Korean Journal of Mycology
• /
• v.44 no.4
• /
• pp.307-313
• /
• 2016

To develop a functional strawberry Makgeolli, we produced Makgeolli using strawberry as an additive and then investigated its physicochemical properties. Among 7 different alcohol-fermenting yeasts, Saccharomyces cerevisiae JSK104 produced 17.4% ethanol on the 7th day of fermentation and was selected for use in the brewing of strawberry Makgeolli. Changes in physicochemical properties, numbers of yeast and lactic acid bacteria, and antihypertensive angiotensin-converting enzyme inhibitory activity were investigated during the fermentation of strawberry Makgeolli. The pH tended to decrease and the total acidity increased as the fermentation period elapsed. The ethanol content reached about 17% on the 7th day after fermentation, and the numbers of yeast and lactic acid bacteria reached a maximum on the 1st day of fermentation and then maintained a constant number. The antihypertensive angiotensin-converting enzyme activity reached a maximum after 5 days of fermentation and then was not significantly changed afterwards.