• Journal of Microbiology
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• v.34 no.4
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• pp.327-333
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• 1996

Yeast, like many other microbes, encounters large variations in ambient pH in their natural environments. Microorganisms capable of growing over a wide pH range require a versatile, efficient pH homeostatic mechanism protecting intracellular processes against extremes of pH. In several organisms, fusions to the bacterial lacZ gene have been extremely useful for the identification of genes expressed at different time during the life cycle or under different growth conditions. In this study, using the lacZ gene screening system, we surveyed a large number of yeast strains with lacZ insertion to identify genes regulated by pH. A yeast genomic library was constructed and inserted with lacZ by a shuttle mutagenesis procedure. The yeast transformants were individually picked up with a toothpick, replica-plated, and grown in alkaline pH medium. Among the 35,000 colonies screened, 10 candidate strains were identified initially by the $\beta$-gal assay. We finally confirmed two yeast strains carrying the genes whose expression are strictly dependent on pH of growth medium. One of the fusions showing a 10-fold induction in expression level in response to alkali pH was selected and further characterized. The pH-regulated gene was cloned by inverse PCR and a partial sequence of the gene was determined. Identification and characterization of the gene is currently under investigation.

• Mycobiology
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• v.48 no.4
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• pp.296-303
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• 2020

Three yeast strains (Hue-1, Hue-8, and Hue-19) with strong heavy metal tolerance were isolated from mangosteen from Hue city, Vietnam. They exhibited identical phenotype and phylogeny. Sequence analysis of the D1/D2 region of the LSU rRNA gene and the internal transcribed spacer (ITS) region demonstrated that the closest relative of these strains is Papiliotrema sp. with 2.12% and 3.55-3.7% divergence in the D1/D2 domain, and ITS domain, respectively. Based on the physiological, biochemical, and molecular data, the three strains belong to a novel species of Papiliotrema genus, for which the name Papiliotrema huenov sp. nov. is proposed. These strains are highly tolerant of heavy metals compared to other yeasts, being able to grow in the presence of 2 mM Pb (II), 2 mM Cd (II), and up to 5 mM Ni (II), but no growth was observed in the presence of 1 mM As (III).

• The Korean Journal of Mycology
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• v.51 no.4
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• pp.361-371
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• 2023

The study was undertaken to isolate and characterize wild yeast strains from soil samples collected in Seoul, Korea. Among the 19 yeast strains obtained, 17 were previously recorded species. The remaining two strains, Wickerhamomyces sp. GW1-4 and Archaeorhizomyces sp. YB4-103 were new species candidates. The genomic and microbiological characteristics of GW1-4 and YB4-103 were investigated. Phylogenetic analyses based on the 26S rRNA gene sequences and internal transcribed sequences, GW1-4 and YB4-103, represent a distinct lineage within the family Phaffomycetaceae and Archaeorhizomycetaceae, respectively. The GW1-4 and YB4-103 strains had the highest sequence homology with Wickerhamomyces xylosivorus NBRC 111553^T (88.97%) and Archaeorhizomyces finlayi CBS 128710^T (87.55%), respectively.

• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.4
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• pp.288-305
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• 2000

A review on the main aspects associated with yeast flocculation and its application in biotechnological processes is presented. This subject is addressed following three main aspects-the basics of yeast flocculation, the development of "new" flocculating yeast strains and bioreactor development. In what concerns the basics of yeast flocculation, the state of the art on the most relevant aspects of mechanism, physiology and genetics of yeast flocculation is reported. The construction of flocculating yeast strains includes not only the recombinant constitutive flocculent brewer's yeast, but also recombinant flocculent yeast for lactose metabolisation and ethanol production. Furthermore, recent work on the heterologous $\beta$-galactosidase production using a recombinant flocculent Saccharomyces cerevisiae is considered. As bioreactors using flocculating yeast cells have particular properties, mainly associated with a high solid phase hold-up, a section dedicated to its operation is presented. Aspects such as bioreactor productivity and culture stability as well as bioreactor hydrodynamics and mass transfer properties of flocculating cell cultures are considered. Finally, the paper concludes describing some of the applications of high cell density flocculating bioreactors and discussing potential new uses of these systems.e systems.

• Microbiology and Biotechnology Letters
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• v.24 no.2
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• pp.143-148
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• 1996

Thousand actinomycetes and 50 soil samples were used for the isolation of microorganisms producing yeast cell wall lytic enzymes. Among 493 strains producing large clear zones on autolysed washed yeast (AWY), 117 strains were selected on living yeast cell agar plates. With the method of lytic activity, one strain (St-1702) was selected, which was temporarily identified as Streptomyces eurythermus. The optimal condition for enzyme production of this strain was partially determined as follows: incubation of the strain for 3 days at 30$\circ$C in the medium containing 2% freeze dried yeast cell, 1% glucose, 1% K$_{2}$HPO$_{4}$, 0.01% MgSO$_{4}$'7H$_{2}$O, 0.5% peptone, and 0.2% (NH$_{4}$)$_{2}$CO$_{3}$ with pH 7.0. The protoplast formation of yeast by using the enzyme produced by this strain was compared with commercial enzymes.

• Korean journal of food and cookery science
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• v.11 no.1
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• pp.9-12
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• 1995

The molar ratio of sterol to phospholipid differed from yeast strains, and the ratio was relatively higher in non-freeze-tolerant yeast strain, S. cerevisiae than freeze-tolerant yeast strains, D$\sub$2-4/ or CFY. Phospholipid composition of these yeast were also investigated. Phosphatidylcholine content was larger among phospholipids in all yeasts. Higher ratio of PC/PE was found in freeze-tolerant yeast than non-freeze-tolerant yeast. Higher proportion of linolein acid(18 : 2) against total fatty acid attached to phospholipid was observed in D$\sub$2-4/ than S. cerevisiae or CFY, and the degree of unsaturation of fatty acid was higher in D$\sub$2-4/ and CFY than in S. cerevisiae. These results suggested that the fluidity of yeast cell membrane was different in yeast strains, which might result in the difference in freeze-injury of yeast at low temperatures.

• Journal of Life Science
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• v.9 no.1
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• pp.22-25
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• 1999

In order to study the mechanism for the adaptation to salt stress, we mutagenized budding yeast Saccharomyces cerevisiae with Ethylmethane sulfonate, and isolated salt-tolerant mutants. Among the salt-tolerant mutants, two strains exhibit additional temperature sensitive phenotype. Here, we report that these two salt-tolerant mutants are specific to {TEX}$Na^{+}${/TEX} rather than general osmotic stress. These mutant strains may contain mutations in the genes involved in {TEX}$Na^{+}${/TEX} home-ostasis.

• 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.

• Microbiology and Biotechnology Letters
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• v.16 no.6
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• pp.443-449
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• 1988

Three yeast strains isolated from various sources were tested in its morphological, physiological, and biochemical characteristics. The results were compared with those of 35 standard yeast strains in order to study important taxonomical characteristics for yeast identification and to find out the problem of computer identifying system. Although few characteristics did not coincide with literature data, three unidentified strains were temporarily identified as Saccharomyces exiguus, Candida edax, and Candida membranaefactence. The use of computer identifying system must be accomponied with conventional identification method because of the restriction of data sources for computer system.

• The Korean Journal of Mycology
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• v.45 no.1
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• pp.23-30
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• 2017

Twenty-two yeast strains of 15 species were isolated from the leaves of 20 trees on Oknyeobong Peak, and 24 yeast strains of 12 species were isolated from the leaves of 20 trees on Yeonjasan Mountain in Daejeon city, Korea. Cryptococcus bestiolae (5 strains) and Aureobasidium pullulans (8 strains) were the predominant isolates from Oknyeobong Peak and Yeonjasan Mountain, respectively. Of a total of 46 yeast strains, Cryptococcus kuetzingii JSL508, Cryptococcus vishniacii JSL509, and Dioszegia takashimae JSL510 from Okyeobong Peak, and Plowrightia periclymeni JSL514, Erythrobasidium hasegawanium JSL0193, and Rhodotorula nothofagi JSL0196 from Yeonjasan Mountain were determined to be yeast strains that were yet unrecorded in Korea. Morphological and cultural characteristics of these unrecorded yeasts were investigated. Erythrobasidium hasegawanium JSL0193 and Rhodotorula nothofagi JSL0196 did not form ascospores and pseudomycelia. All the strains, except Dioszegia takashimae JSL510, were halotolerant or halophilic, and Cryptococcus kuetzingii JSL508 and Dioszegia takashimae JSL510 were thermophilic, growing at $37^{\circ}C$.