• Journal of Microbiology and Biotechnology
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• v.1 no.1
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• pp.6-11
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• 1991

This study deals with investigation of the ethanol tolerance of yeast strains with respect to fatty acid composition and intracelluar ethanol concentration during alcohol fermentation. The cell viabilities and fermentation abilities of Saccharomyces cerevisiae and Kluyveromyces fragilis were improved by aeration and addition of unsaturated fatty acids into growth medium. Aeration decreases the accumulation of ethanol, while increases unsaturated fatty acid contents inside yeast cells. Thus it was found that oxygen and unsaturated fatty acids play decisive roles in the increase of ethanol tolerance of yeasts.

• Journal of Species Research
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• v.10 no.4
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• pp.344-349
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• 2021

The purpose of this study was to isolate and identify wild yeasts from soil of Gyeongju city, and Haemadipsa rjukjuana of Gageodo Island, characterizing unrecorded yeast strains from Korea. The molecular analysis of the D1/D2 domain of 26S rDNA of yeast was performed using the Basic Local Alignment Search Tool (BLAST). No official report exists describing these three species: one species in the genus Candida, one species in the genus Debaryomyces, and one species in the genus Solicoccozyma. Candida saitoana YL9, Debaryomyces fabryi YL1, and Solicoccozyma terrea 20g9-1 are recorded for the first time from Korea. All three strains were oval shaped and polar binding, while positive for glucose, ᴅ-xylose, and ᴅ-cellobiose. Morphological, physiological, and biochemical properties are described in the species descriptions.

• The Korean Journal of Mycology
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• v.48 no.4
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• pp.523-531
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• 2020

This study focused on the isolation and characterization of wild yeasts in Korea. The yeasts were identified by phylogenetically analyzing the D1/D2 domains of the 26S rDNA regions. Consequently, we identified seven strains, NNIBRFG856, NNIBRFG3732, NNIBRFG3734, NNIBRFG3738, NNIBRFG3739, NNIBRFG5497, and NNIBRFG6049, which were confirmed to be Kabatiella microsticta, Pichia membranifaciens, Candida vartiovaarae, Candida sake, Debaryomyces hansenii, Candida railenensis, and Schwanniomyces polymorphus, respectively, all of them being new in Korea. Morphological and cultural characteristics of these yeast species were investigated. None of the strains formed ascospores or pseudomycelia. Moreover, these yeasts grew in a pH range of 4-8. NNIBRFG3732, NNIBRFG3738, NNIBRFG3739, NNIBRFG5497, and NNIBRFG6049 were halotolerant or halophilic, and NNIBRFG3732, NNIBRFG3734, and NNIBRFG6049 grew in vitamin-free medium. NNIBRFG3732, NIBRFG3739, and NNIBRFG6049 grew at 35 ℃, but not at 40 ℃.

• Journal of Microbiology and Biotechnology
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• v.22 no.7
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• pp.960-966
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• 2012

The diversity and composition of yeast populations may greatly impact wine quality. This study investigated the yeast microbiota in two different types of wine fermentations: direct inoculation of a commercial starter versus pied de cuve method at an industrial scale. The pied de cuve fermentation entailed growth of the commercial inoculum used in the direct inoculation fermentation for further inoculation of additional fermentations. Yeast isolates were collected from different stages of wine fermentation and identified to the species level using Wallersterin Laboratory nutrient (WLN) agar followed by analysis of the 26S rDNA D1/D2 domain. Genetic characteristics of the Saccharomyces cerevisiae strains were assessed by a rapid PCR-based method, relying on the amplification of interdelta sequences. A total of 412 yeast colonies were obtained from all fermentations and eight different WL morphotypes were observed. Non-Saccharomyces yeast mainly appeared in the grape must and at the early stages of wine fermentation. S. cerevisiae was the dominant yeast species using both fermentation techniques. Seven distinguishing interdelta sequence patterns were found among S. cerevisiae strains, and the inoculated commercial starter, AWRI 796, dominated all stages in both direct inoculation and pied de cuve fermentations. This study revealed that S. cerevisiae was the dominant species and an inoculated starter could dominate fermentations with the pied de cuve method under controlled conditions.

• Journal of the East Asian Society of Dietary Life
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• v.7 no.4
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• pp.538-544
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• 1997

To utilize abundant poor persimmon fruits effectively, It was studied on alcohol fermentation strains which were isolated and indentified from poor persimmon fruits. The strains which had exellent alcohol production ability were analysized morphogical, cultural characteristics and identified Saccharomyces cerevisiae YJK 20, Sacachromyces kluveri DJ 97. Alcohol production ability between the isolated strains and industrial alcohol yeasts was compared in the YPD medium, persimmon extract medium. Isolated strains had high alcohol production ability in both of two medium, respectively. So it was expected that the strains. YKJ 20 and DJ 97 had good alcohol fermentation ability of persimmon fruits.

• Journal of Microbiology and Biotechnology
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• v.20 no.9
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• pp.1314-1321
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• 2010

Sulfur metabolism in S. cerevisiae is well established, but the mechanisms underlying the formation of sulfide remain obscure. Here, we investigated by real-time RT-PCR the dependence of expression levels of MET3, MET5/ECM17, MET10, MET16, and MET17 along with SSU1 on nitrogen availability in two wine yeast strains that produce divergent sulfide profiles. MET3 was the most highly expressed of the genes studied in strain PYCC4072, and SSU1 in strain UCD522. The strains behaved differently according to the sampling times, with UCD522 and PYCC4072 showing the highest expression levels at 120 h and 72 h, respectively. In the presence of 267 mg assimilable N/l, the genes were more highly expressed in strain UCD522 than in PYCC4072. MET5/ECM17 and MET17 were only weakly expressed in both strains under any condition tested. MET10 and SSU1 in both strains, but MET16 only in PYCC4072, were consistently upregulated when sulfide production was inhibited. This study illustrates that strain genotype could be important in determining enzyme activities and therefore the rate of sulfide liberation. This linkage, for some yeast strains, of sulfide production to expression levels of genes associated with sulfate assimilation and sulfur amino acid biosynthesis could be relevant for defining new strategies for the genetic improvement of wine yeasts.

• Food Science and Preservation
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• v.7 no.2
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• pp.228-232
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• 2000

To utilize abundant potatoes effectively, it was studied on alcohol fermentation strains which were isolated and identified. Fifteen yeast strains with high alcohol fermentation ability were isolated from rotted potatoes. Among them, two isolated strains, 5-3A and 10-4B showing the highest alcohol fermentation ability were identified as Zygosaccharomyces fermentati based on the morphological and physiological characteristics. Their optimum conditions for the alcohol fermentation in 25% glucose were pH 3.0, 30$^{\circ}C$ and 150 rpm of shaking speed, respectively.

• Microbiology and Biotechnology Letters
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• v.25 no.3
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• pp.266-270
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• 1997

From persimmon fruits, about 40 yeast strains were isolated and tested for their ability of alcohol fermentation were tested. Among them, two strains, RCY14 and RCY15, showing the highest alcohol fermentibility were selected for further investigations. They were identified as Saccharomyces cerevisiae and Saccharomyces kluyveri based on their morphological, cultural and physiological properties. Their optimum condition for the alcohol fermentation in YPD-15% glucose was pH 6.0, 30$circ$C and 120 rpm of shaking speed. The alcohol yields of S. cerevisiae RCY14 and S. kluyveri RCY15 in a persimmon juice were 94.54 and 96.81%, respectively. Although the alcohol yields of both strains were not very high in YPD-15% glucose, they were much higher in a persimmon juice as compared to those of S. cerevisiae Balyon-1, S. cerevisiae 701 and S. cerevisiaein W3 which are being used in the industrial alcohol fermentation.

• Microbiology and Biotechnology Letters
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• v.43 no.1
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• pp.56-64
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• 2015

It has been known for some time to the wine industry that non-Saccharomyces yeasts play an important role in increasing volatile components through the secretion of extracellular enzymes. The objective of this study was to investigate what types of enzymes are produced by 1,007 non-Saccharomyces yeast strains isolated from Korean fermented foods. Among 1,007 yeast strains, the 566, 45 and 401 strains displayed β-glucosidase, glucanase and protease activity, respectively. In addition, the 563 and 610 strains possessed tolerances against cerulenin and TFL, and the 307 strain was tolerant to 15% ethanol. Yeasts producing harmful biogenic amines and hydrogen sulfide were excluded from further study, and eventually 12 yeast strains belonging to the genera Wickerhamomyces, Hanseniaspora, Pichia, Saccharomyces were identified, based on the 26S rRNA gene sequences. Among the 12 strains, the 9 and 5 strains possessed glucose and ethanol tolerance, respectively. Yeasts belonging to the genus Saccharomyces produced more than 8% alcohol, but non-Saccharomyces yeasts produced only 3% alcohol.

• Food Science and Biotechnology
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• v.17 no.3
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• pp.558-563
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• 2008

To prevent weakly flocculating characters of bottom brewing yeast during first fermentation, various technical investigations were carried out using strain of Saccharomyces cerevisiae. It appeared that the propagation at $10^{\circ}C$ promoted the molecular structure and biochemical composition of cell wall in favor of flocculation. The yeast grown at $20^{\circ}C$ by addition of zinc ion also had a stimulating effect on flocculation behavior during first fermentation cycle. The zinc ion did not influence directly on the changes of cell wall in favor of stronger flocculence. The increased fermentation activity of yeast due to addition zinc ion was rather responsible for the intensified flocculation capacity. It was concluded that the weakly flocculating characters of bottom brewing yeast during first fermentation can be solved by using yeast propagated at $10^{\circ}C$ or by means of yeast by addition of zinc ion during propagation.