• Mycobiology
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• v.39 no.1
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• pp.33-39
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• 2011

Wild yeasts on the surface of various fruits including grapes were surveyed to obtain yeast strains suitable for fermenting a novel wine with higher alcohol content and supplemented with rice starch. We considered selected characteristics, such as tolerance to alcohol and osmotic pressure, capability of utilizing maltose, and starch hydrolysis. Among 637 putative yeast isolates, 115 strains exhibiting better growth in yeast-peptone-dextrose broth containing 30% dextrose, 7% alcohol, or 2% maltose were selected, as well as five ${\alpha}$-amylase producers. Nucleotide sequence analysis of the 26S rDNA gene classified the strains into 13 species belonging to five genera; Pichia anomala was the most prevalent (41.7%), followed by Wickerhamomyces anomalus (19.2%), P. guilliermondii (15%), Candida spp. (5.8%), Kodamaea ohmeri (2.5%), and Metschnikowia spp. (2.5%). All of the ${\alpha}$-amylase producers were Aureobasidium pullulans. Only one isolate (NK28) was identified as Saccharomyces cerevisiae. NK28 had all of the desired properties for the purpose of this study, except ${\alpha}$-amylase production, and fermented alcohol better than commercial wine yeasts.

• Journal of Microbiology and Biotechnology
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• v.4 no.3
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• pp.215-221
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• 1994

Two strains of yeast (RA-74-2 and RA-912) showing superior fermenting ability at a high temperature were isolated from soils and wastewaters by an enrichment culture method. Based on the morphological and physiological charateristics, the two strains were identified as Saccharomyces cerevisiae and Kluyveromyces marxianus, respectively. RA-74-2 was able to grow upto $43^{\circ}C$ and sustain similar fermenting ability in the temperatures range from 30 to $40^{\circ}C$. In addition, the sugar- and ethanol-tolerance of RA-74-2 were 30% (w/v) glucose and 10% (v/v) ethanol, which appeared to be higher than those of nine other industrial yeast strains currently being used in the alcohol factories. The thermotolerant ethanol fermenting yeast RA-912 showed identical growth in the temperatures range from 35 to $45^{\circ}C$ and was resistant to various heavy metals. The quality and quantity of byproducts of the isolated yeast strains in fermentation broth after fermentation at $40^{\circ}C$ and $45^{\circ}C$ were similiar with those obtained at $30^{\circ}C$. These results show that RA-74-2 can be adopted for the ethanol fermentation process where the expenses for cooling system is significant, and suggest that RA-912 may be applied in either SSF(simultaneous saccharification and fermentation) or Flash-fermentation process and RA-912 may be used as a gene donor for the development of thermotolerant ethanol-fermenting yeasts.

• The Korean Journal of Mycology
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• v.45 no.3
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• pp.234-240
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• 2017

The goal of this study was to isolate wild yeasts from reed fields in the Seocheon-gun county in Chungcheongnam-do, South Korea. Molecular analysis of the D1/D2 domain of the 26S rDNA of the yeasts isolated from soil samples was performed using Basic Local Alignment Search Tool (BLAST). In total, 20 yeast strains from 11 species were isolated from 20 different soil samples. Candida species were observed to be the most common yeasts. Of these 20 strains, Candida subhashii (6 strains), Candida tropicalis (3 strains), Candida boleticola MS008, and Lachancea thermotolerans (2 strains) were identified as alcohol-fermenting yeasts. Further, Bullera japonica YJ10-1, Candida subhashii J7-1, Kluyveromyces yarrowii YJ11-1, and Ustilago shanxiensis Y10-1 were newly recorded yeast strains in Korea, and therefore, their microbiological characteristics were investigated further. All of these unrecorded yeast strains had oval cells; only Candida subhashii J7-1 formed ascospores and pseudomycelia. Kluyveromyces yarrowii YJ11-1 grew in vitamin-free medium, and all of these strains, except Candida subhashii J7-1, grew in 5% NaCl-containing YPD broth.

• Korean Journal of Food Science and Technology
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• v.30 no.1
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• pp.161-167
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• 1998

Whey is by-product from natural cheese manufacturing process. For alcoholic fermentation, the initial lactose content and pH were adjusted to 4.5% and 4.2, respectively. Two strains of yeasts (Kluyveromyces marxianus, Saccharomyces cerevisiae) and seven strains of lactic acid bacteria (Lactobacillus brevis, Lactobacillus casei, Lactobacillus acidophilus, Lactobacillus lactis, Leuconostoc cremoris, Lactococcus lactis and Streptococcus thermophilus) were examined for their alcohol production and sensory acceptability. Ethanol content in the whey fermented by lactose-fermenting K. marxianus was 2.8% at 4th day of incubation and that fermented by nonlactose fermenting S. cerevisiae was 0.2%. In case of mixed fermentation with yeasts and tactic acid bacteria (LAB being inoculated at 0 hr), the maximum ethanol production was obtained in the sample inoculated at 16 hr by s. cerevisiae, and in the sample inoculated at 24 hr by K. marxianus. The optimum temperature was $37^{\circ}C$ for alcohol production under static condition. The production of $CO_2$ gas was higher in the whey fermented by K. marxianus (1.88%) than by S. cerevisiae (0.04%). The titratable acidity of the whey gradually increased with fermentation time and its content was 0.39% at 4th day of fermentation by K. marxianus and 0.52% by S. cerevisiae. Among seven strain of latic acid bacteria tested, Lactococcus lactis exerted synergistic effect for acid production with K. marxianus. Therefore, overall results suggestd that the combination of Lactococcus lactis and K. marxianus was best choice in fermenting cheese whey for edible purpose.

• Korean Journal of Agricultural Science
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• v.12 no.2
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• pp.272-281
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• 1985

The ginseng extract was investigated for their effects on the fermentation of Kluyveromyces fragilis IFO 0288, and the addition of 0-5.0% of ginseng extract from skim milk media were compared to its effects during suspension culture at $30^{\circ}$ for 168 hours. The results are summarized as follows; 1. The addition of 1.0% and 5.0% ginseng extract were significantly increased pH and acidity compared to control. 2. $CO_2$ evolution was significantly in 1.0% but inhibited in 5.0% ginseng extract 3. Alcohol production was more producted and shortened of fermentation time in 1.0-5.0% than 0-0.5% added groups. 4. The number and growth rates of yeast was shortened inductive phase and lengthened extinctive phase in 1.0-5.0% added groups. 5. Free sugar contained in ginseng extract was not significantly affected by fermentation of yeasts.

• Korean Journal of Food Science and Technology
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• v.41 no.5
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• pp.541-546
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• 2009

The objectives of this study were to evaluate the physico-chemical and sensory characteristics of a Korean traditional alcoholic beverage (yakju) prepared using different nuruk (Korean-style koji) concentrations and yeasts such as the fusant FA776 and Saccharomyces cerevisiae KOY-1, respectively. The fusant FA776, which has alcohol-fermenting and starch-utilizing properties, was formed by Saccharomyces cerevisiae KOY-1 and Saccharomyces diastaticus KCTC1804. The fermentation trial was conducted in a 5 L lab-scale jar at $25^{\circ}C$. The maximum alcohol production of the K-100 and F-50 reached levels of 135.0 mg/mL and 119.4 mg/mL, respectively. The pH values were in a range of 4.3-4.5. Total acidity was in a range of 0.47-0.60%. Organic acids and amino acids were analyzed in order to evaluate variations in its composition and content via HPLC analysis. Organic acids including lactic acid, citric acid, malic acid, and pyruvic acid, and 16 kinds of amino acids, including aspartic acid, were detected in all treatments. K-100 showed the highest amino acid contents, whereas F-50 exhibited the lowest amino acid contents. Volatile flavor components such as phenylethyl alcohol, isoamyl alcohol, 2-methylthiophane, isobutyl alcohol, and ethyl succinate were detected as a major component in all treatments, as determined via gas chromatography. The results of our sensory evaluation demonstrated that Yakju fermented by the FA776 fusant yielded more favorable results than S. cerevisiae KOY-1.

• Food Science and Preservation
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• v.20 no.6
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• pp.886-893
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• 2013

Several indigenous sulfite-resistant yeasts were isolated at the microbial succession stage of yeast flora during spontaneous fermentation of Campbell Early grapes using a YPD plate that contained 200 mg/L or 500 mg/L potassium metabisulfite. When they were applied to the wine fermentation using the Campbell Early grape and apple juices, strains S13 and D8 showed strong alcohol fermentation and good flavor production. They were identified as Saccharomyces cerevisiae in the phylogenetic analysis based on their ITS 1-5.8S-ITS II DNA sequences. The two yeast strains grew to a high cell density in the YPD media supplemented with 40%(w/v) glucose. They also grew rapidly in the YPD media at $40^{\circ}C$. While strain S13 showed some differences in cell density at the two temperatures, no marked difference was observed during the culture of strain D8. The strains grew relatively well at pH 5.0 and 9.0 compared with pH 7.0, which was the optimum pH for their growth. Especially, strain S13 cultivated in the YPD media at pH 9.0 grew to 93% of the growth of strain D8, which was obtained at pH 7.0.

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

• Korean Journal of Microbiology
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• v.28 no.1
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• pp.55-64
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• 1990

Cell volume and DNA contents of the fusants were similar to those of parents. Genetic stability of the fusants was increased when they were cultured on minimal medium (MM) rather than on complete medium (CM), and the fusants were stabilized by subculturing 7 generations each 7 day on MM agar. The finally selected fusants after being cultured for 6 months on CM were stable without segregation. The fusants could also form nuclein and ascospores, and show red and pink colors by the test of TTC colorization. Assimilability and fermentability of carbon sources of the fusants were similarto those of parents. The tolerance of KCl, NaCl, sodium propionate and cycloheximide showed the traits of one strain of parents. When the fusants were cultured for 72 hr and 60 hr in the medium containing 20% glucose and sucrose, respectively, the yield of ethanol for FWKS 260 was reached to 9.6 v/v% and 9.8v/v%, respectively. The sensitive strain Kyokai 7 was found to be killed entirely after cultivation of 48 hr by the killer toxin from the fusants. The recipient S 29 and Kyokai 7 were found to have neither L nor M dsRNA plasmid. However, K 52 and fusants had both L and M dsRNA plasmid of 4.7 kb and 2.5 kb, respectively. The curants treated by heat and cycloheximide did not contain M dsRNA plasmid, but had large amounts of L dsRNA plasmid of those of killer yeasts.