• Preventive Nutrition and Food Science
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• 제1권2호
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• pp.252-255
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• 1996

As an index of freeze-injury of yeast, the leakage of intracellular substances from yeast cells after freeze-thawing was investigated. It was found that much more ultraviolet-absorbing substances leaked out from non-freeze tolerant yeast (NETY) than from freeze-tolerant yeast. Furthermore, the rate of leakage of cellular substances form NFTY during incubation exceeded that of FTY, indicating that NFTY is more susceptible to freeze-injury than FTY during frozen-storage. An apparent degradation of phospholipid was observed during incubation of perfermented frozen-cells of NFTY, while little change of phospholipid occurred in FTY, These results suggested that the difference in the sensitivity of yeast might be due to the strength of cell membrane in terms of the degradation of phospholipid by enzymes, phospholipases, attached to cell membranes.

• Food Science and Biotechnology
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• 제17권3호
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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.

• Food Science and Preservation
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• 제5권2호
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• pp.186-190
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• 1998

In order to investigate the possible application of immobilized yeast cells in sparkling wine production instead of riddling puns by the traditional method, fermentation characteristics were tested during the sparkling wine fermentation in the bottle using immobilized yeast cells with alginate. The rates of sugar consumption and alcohol production were faster with free cells than those with immobilized cells during the fermentation. The higher concentration of yeast cells and the lower concentration of alginate in the cell immobilization resulted in the faster sugar consumption and alcohol production. It also resulted in the increase of yeast cell concentration released from immobilized beads during the fermentation. However, no differences were shown in the contents of alcohol, residual sugar and CO2 pressure after fermentation. In case concentration of yeast cells released from immobilized beads during bottle fermentation, the higher concentration of alginate had and the lower had.

• Korean Journal of Food Science and Technology
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• 제29권5호
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• pp.1021-1027
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• 1997

We examined some properties of yeast cell wall lytic enzyme produced by Dicyma sp. YCH-37. Several metal ions, reducing reagents, and chemical modifiers have little effects on the lytic activity, except guanidine-HCl. Yeast cells of early log phase were more susceptible to the enzyme than those of stationary phase, and heat-treated cells were more easily lysed than intact living ones. Yeast cells pretreated with organic solvents such as butanol and acetone were more susceptible to the enzyme than intact living ones. Yeast cells cultured in Yeast extract-Malt extract medium containing 0.5 M ammonium sulfate were easily lysed by the lytic enzyme, and yeast cells cultured without shaking were more easily lysed by the enzyme than those with shaking. When SDS, ${\beta}-mercaptoethanol$, Triton X-100, sodium sulfite, and KCl were added to enzyme reaction mixture each, lysis of yeast cells was more effective.

• Journal of Microbiology and Biotechnology
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• 제14권3호
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• pp.470-473
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• 2004

In the yeast Saccharomyces cerevisiae, iron can be toxic. Because of this phenomenon, its metabolism of iron is strictly regulated. We have constructed a model system in which cell growth is defected during periods of iron over-load. When $Aft1-1^{up}$ protein was overexpressed with Ga110 promoter, a galactose inducible promoter, cell growth was defected and levels of CLN2 transcript decreased. However transcript levels of AFT1 and FET3 genes increased over time in a consistent manner throughout the course of $AFT1-1^{up}$ overexpression. We have screened to find genes to suppress cell growth defect by iron overload with YEp-derived high copy yeast genomic DNA library and found that high copy of Rmelp suppressed cell growth defects. Rme1p has been known as an activator protein of CLN2 gene expression. Taking these results together, we suggest that the yeast cell cycle is arrested at the $G_1$, phase by iron overload via Cln2p.

• KSBB Journal
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• 제14권2호
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• pp.181-187
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• 1999

We have investigated industrial media for lactic acid fermentation to reduce the cost of nitrogen sources. Corn steep liquor (CSL) was successfully used at 5% (v/v) in batch fermentations. Use of soluble CSL improved the productivity about 20% with an advantage of clearer fermentation broth. Yeast extract-complemented CSL improved the productivity about 20% with an advantage of clearer fermentation broth. Yeast extract-complemented CSL media further increased the increased the productivity. It was found that 3.1 g/L yeast extract and 5% CSL could be an effective substitute for 15 g/L yeast extract in 10% glucose medium. Brewing yeast was also used as a sole nitrogen source equivalent to 5% CSL. A continuous culture coupled with cell-recycle by microfiltration at the dilution rate of 0.05-0.065 h-1 led to the highest lactic acid productivity. Lactic acid was recovered by electrodialysis from the cell free broth. Depleted cell free broth supplemented with 5-10 g/L of yeast extract performed reasonably in batch and continuous cultures. Reuse of the fermentation broth may reduce the cost of raw materials as well as minimize the fermentation wastes.

• KSBB Journal
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• 제21권6호
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• pp.479-483
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• 2006

[ ${\beta}-Glucan$ ], one of the cell wall components, is most plentiful polysaccharides in cell wall and has several advantages in immune system. In yeast ${\beta}-glucan$ is mainly contained in the yeast cell wall, and thus it is important to produce high levels of cell mass for the mass production of yeast ${\beta}-glucan$. The best carbon and nitrogen sources on cell mass production were high fructose syrup and yeast extract. Response surface methodology (RSM) was very potential tool for the optimization of process factor and medium component. It was applied to estimate the effects of medium components on the production of cell mass. Optimal concentrations of high fructose syrup and yeast extract by response surface methodology were 8.0% (v/v) and 5.2% (w/v), respectively and the cell mass predicted was $17.0\;g/{\ell}$ at 20 h of cultivation.

• Journal of Microbiology
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• 제35권2호
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• pp.149-151
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• 1997

A plasmid vector with combined features of yeast shuttle vector and mammalian expression vector was constructed to facilitate expression of cloned gene in both cell-types. All necessary elements required for plasmid maintenance and selection in E. coli, yeast and mammalian cells were size-economically arranged in this plasmid. The numan cytomegalovirus (CMV) immediate early promoter and yeast GAL1 promoter were sequentially placed in front of the gene to be expressed. The synthetic splicing donor and acceptor sequences were inserted into the immediate upstream and downstream of the GAL1 promotor, allowing the CMV promotor to direct the expression of a given gene in mammalian cell environment by splicing out the interfering GAL1 promotor sequence. When the resulting vector containing LacZ as a gene was introduced into yeast and mammalian cells, both cells efficiently produced .betha.-galactosidase, dimonstrating its dual host usage.

• Journal of Microbiology and Biotechnology
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• 제16권2호
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• pp.247-255
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• 2006

Yeast cell wall matrix particles are composed entirely of mannoprotein and ${\beta}-glucan$. The mannoproteins of yeast cell wall can systemically enhance the immune system. We previously purified and analyzed alkali-soluble ${\beta}-glucans$ [${\beta}$-(1,3)- and ${\beta}$-(1,6)-glucans] [10]. In the present study, a wild-type strain was first mutagenized with ultraviolet light, and the cell wall mutants were then selected by treatment with 1.0 mg/ml laminarinase (endo-${\beta}$-(1,3)-D-glucanase). Mannoproteins of Saccharomyces cerevisiae were released by laminarinase, purified by concanavalin-A affinity and ion-exchange chromatography. The results indicated that the mutants yielded 3-fold more mannoprotein than the wild-type. The mannoprotein mass of mutant K48L3 was 2.25 mg/100 mg of yeast cell dry mass. Carbohydrate analysis revealed that they contained mannose, glucose, and N-acetylglucosamine. Saccharomyces cerevisiae cell wall components, mannoproteins, are known to interact with macrophages through receptors, thereby inducing release of tumor necrosis factor alpha ($TNF-{\alpha}$) and nitric oxide. Mannoprotein tractions in the present study had a higher macrophage activity of secretion of $TNF-{\alpha}$ and nitric oxide and direct phagocytosis than positive control ($1{\mu}g$ of lipopolysaccharide). In particular, F1 and F3 fractions in mannoproteins of K48L3 enhanced and upregulated the activity of nitric oxide secretion and macrophage phagocytosis by approximately two- and four-fold, respectively.

• Journal of Life Science
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• 제15권6호
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• pp.923-927
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• 2005

ln order to develop yeast cells that produce a bacteriocin on their cell surfaces, the 114 bp Leucocin A gene with stop codon was ligated into pYDl, an yeast vector. The recombinant DNA, pYDl-LeucoA was used to transform yeast (Saccharomyces cerevisiae) cells. Yeast cells harboring pYDl-LeucoA showed antibacterial activity against Bacillus subtilis. To confirm these bacteriocidal yeast cells possess the Leucocin A gone, PCR was performed with plasmid prepared from transformed yeast cells as a template and two Leucocin A-specific primers. In this study, bacteriocidal yeast cells that can be used as an antibiotic or a food preservative were developed.