• Analytical Science and Technology
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• 제35권4호
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• pp.181-188
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• 2022

This paper describes a comparative analysis of yeast cell viability at exponential and stationary growth phases using multiple conventional techniques and statistical tools. Overall, cellular responses to various viability assays were asynchronous. Results of optical density measurement and direct cell counting were asynchronous both at exponential and stationary phases. Proliferative capacity measurement using SP-SDS indicated that cells at the end of the stationary phase were proliferative as much as exponentially growing cells. Metabolic activity assays using two different dyes concluded that the inside of cells at stationary phase is slightly less reducing compared to that of exponentially growing cells, implying that the metabolic activity imperceptibly declined as cells were aged. These results will be helpful to understand the details of yeast cell viability at exponential and stationary growth phases.

• Journal of Microbiology and Biotechnology
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• 제30권1호
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• pp.54-61
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• 2020

Saccharomyces boulardii is the only probiotic yeast with US Food and Drug Administration approval. It is routinely used to prevent or treat acute diarrhea and other gastrointestinal disorders, including the antibiotic-associated diarrhea caused by Clostridium difficile infections. The formation of reactive oxygen species (ROS), specifically H₂O₂ during normal aerobic metabolism, contributes to programmed cell death and represents a risk to the viability of the probiotic microbe. Moreover, a loss of viability reduces the efficacy of the probiotic treatment. Therefore, inhibiting the accumulation of ROS in the oxidant environment could improve the viability of the probiotic yeast and lead to more efficacious treatment. Here, we provide evidence that supplementation with a non-reducing disaccharide, namely trehalose, enhanced the viability of S. boulardii exposed to an oxidative environment by preventing metacaspase YCA1-mediated programmed cell death through inhibition of intracellular ROS production. Our results suggest that supplementation with S. boulardii together with trehalose could increase the viability of the organism, and thus improve its effectiveness as a probiotic and as a treatment for acute diarrhea and other gastrointestinal disorders.

• Nutrition Research and Practice
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• 제1권4호
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• pp.260-265
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• 2007

Preservation methods on the physiological and brewing technical characters in bottom and top brewing yeast strains were investigated. The preserved yeasts were reactivated after 24 months storage and grown up to stationary phase. The samples of filter paper storage indicated a higher cell growth and viability during propagation than those of nitrogen and lyophilization storage independent on propagation temperature. In addition, the filter paper storage demonstrated a faster absorption of free amino nitrogen and a highest level of higher aliphatic alcohols production during propagation than other preservation methods, which can be attributed to intensive cell growth during propagation. Moreover, the filter paper storage showed a faster accumulation for glycogen and trehalose during propagation, whereas, in particular, lyophilization storage noted a longer adaptation time regarding synthesis of glycogen and trehalose with delayed cell growth. In beer analysis, the filter paper storage formed an increased higher aliphatic alcohols than control. In conclusion, the preservation of filter paper affected positively on yeast growth, viability and beer quality independent on propagation temperature. In addition, in this study, it was obtained that the HICF and Helm-test can be involved as rapid methods for determination of flocculation capacity.

• KSBB Journal
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• 제14권5호
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• pp.561-565
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• 1999

Optimum conditions for vacuum-drying ad cultivation of yeast cells for the production of active dry yeast were examined. At lower temperature, more drying time was required to dry the yeast pellet to reach the desirable water content(8%). Optimum temperature of vaccum oven and time for drying was 63$^{\circ}C$ and 90 min, respectively. Optimum medium composition for flask culture using cane molasses as the substrate were 0.25% sugar, 0.013% $K_2$HPO$_4$, 0.1% $K_2$HPO$_4$. and 0.125% (NH$_4$)$_2$SO$_4$. Culture temperature $25^{\circ}C$ gave the highest survival rate of dired yeast. After finishing fed-batch culture and the culture was left in the fermentor without adding any sugar or nutrient, survival of the dried yeast harvested from the fermentor increased to 86.0% after 36 hr. It was also observed that the yeast cells with higher budding rates showed lower survival rate.

• Asian-Australasian Journal of Animal Sciences
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• 제16권7호
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• pp.1011-1014
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• 2003

The objective of this work was to evaluate a thermotolerant yeast Issatchenkia orientalis DY252 as a microbial feed additive for ruminants. In the present study, the influence of volatile fatty acids (VFA) and temperature on oxygen uptake rate by I. orientalis DY 252 was investigated. It was evident that the oxygen uptake rate was decreased gradually as the VFA concentrations increased in a range of 30 to 120 mM. Although the oxygen uptake rate was not greatly affected by temperature in the range 37 to $43^{\circ}C$, a maximum value of $0.45mg\;O_2/g$ cell/ min was obtained at $39^{\circ}C$. With regard to the oxygen uptake rate by yeast, viability was found to be less important than the metabolic activity of yeast.

• KSBB Journal
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• 제4권2호
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• pp.167-171
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• 1989

The alcohol fermentation using glucose and lactose was carried out to study the effect of fermentation temperature on the ethanol tolerance of Saccharomyces cerevisiae STV89 and Kluyveromyces fragilis CBS397. The maximum specific growth rate and ethanol production rate were increased up to 35$^{\circ}C$ with the fermentation temperature, although maximum ethanol and cell concentration were decreased by increasing the fermentation temperature. The cell viability was also improved by lowering the fermentation temperature. Under the experimental conditions, the best ethanol tolerance of yeast strains was obtain at $25^{\circ}C$. The ethanol tolerance of S. cerevisiae is better than that of K. fragilis at the same fermentation condition. With respect to the carbon source, glucose is found to be more favorable for ethanol tolerance of K. fragilis than lactos.

• Korean Journal of Food Science and Technology
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• 제33권2호
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• pp.205-208
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• 2001

The bitterness of brewers yeast slurry decreased by washing with mild caustic soda solution followed by washing with 0.85% (w/v) NaCl solution The higher concentration of caustic soda was, the lower the bitterness unit(BU) of washed yeast slurry was. The lethal rate of yeast cells increased. When the concentration of caustic soda solution increased from 0.05%(w/v) to 0.25%(w/v), the BU of brewers yeast slurry was decreased from 45 to 3, but yeast cells viability decreased from 93% to 0%. The optimum washing conditions of brewers yeast slurry were as follows: the concentration of caustic soda solution was $0.07{\sim}0.1%$(w/v) and the contact time of brewers yeast slurry with caustic soda was $10{\sim}20$ minutes. The similar washing effect was obtained when the brewers yeast slurry was washed with 20%(v/v) ethanol solution.

• Journal of Microbiology and Biotechnology
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• 제7권1호
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• pp.75-80
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• 1997

An ethanolic fermentation process was developed for preparing Doenjang with high ethanol. Higher and efficient viable cell production of salt-tolerant ethanolic yeast is a prerequisite for the successful commercial-scale process of ethanol production during Doenjang fermentation. Culture conditions of salt-tolerant yeast, S. cerevisiae KFCC 10823, was studied in terms of the effect of several environmental and nutritional factors. Viable cell numbers were the highest in a medium containing the following components per liter of water: soysauce, 300ml; dextrose, 50 g; beef extract, 5 g; yeast extract, 5 g; $KH_2PO_4$, 5 g; NaCl, 50 g. The optimal culture conditions of S. cerevisiae KFCC 10823 were pH 5.5, $25^{\circ}C$, 200 rpm and 0.5 vvm. Yeast viability during batch fermentation was gradually decreased to a level less than $90{\%}$ after 35 hours. The maximum cell number was $2.2{\times}10_7$ cells/ml at the optimal condition. Doenjang prepared with ethanolic yeast was ripened after 45 days at $30^{\circ}C$. This Doenjang contains 470 mg% of amino nitrogen and 2.5% ethanol. The shelf-life at $30^{\circ}C$ was theoretically estimated as 444 days.

• Applied Biological Chemistry
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• 제48권3호
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• pp.246-251
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• 2005

The aim of this study was to evaluate an efficacy about activation on macrophage, using model that measured cell viability, nitric oxide (NO), iNOS (inducible nitric oxide synthase) expression and tumor necrosis $factor-{\alpha}$ ($TNF-{\alpha}$) on Raw 264.7 cells following treatment of Germanium-fortified Yeast in 0, 5, 10, 25, 50, 100, $200\;{\mu}g/ml$ and the same concentration of dried yeast without germanium. Cell viability (%) and NO produced in activated-macrophage were dose-dependant, a significant increase of the cell viability (132.5%) and NO in $10\;{\mu}g/ml$ (p < 0.05). Increase in iNOS level was in $10\;{\mu}g/ml$. $TNF-{\alpha}$ was produced dose-dependant, e.g. in activated-macrophage with a significant increase of the $TNF-{\alpha}$ in 5 and $10\;{\mu}g/ml$ (p < 0.05). Therefore, Germanium-fortified Yeast had an efficacy of NO mediated iNOS and $TNF-{\alpha}$ production by activated macrophage. This result showed that Germanium-fortified Yeast induced activation of cellular immunity, returned to normalcy on injured immune system and procured anticancer system by activation of macrophage, which was important in immune and anticancer function.

• Korean Journal of Microbiology
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• 제37권4호
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• pp.312-316
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• 2001

To improve the ethanol fermentability, four Saccharomyces yeast strains with efficient ethanol fermentability were subjected to rare-mating and protoplast fusion. Using these 4 strains, 5 different combinations of mating-pair or fusion-pair were constructed and their hybrids or fusants were obtained. From the statistical analysis of the results of the ethanol fermentation by the hybrids of the different mating-pair or fusion-pair, no difference was found in ethanol production, but [S. kluveri $khl{\times}S$ cerevisiae cp3] pair was shown to be the best combination which can produce high cell-viability. In fact, the clone No. 3 of the [S. kluveri $khl{\times}S$ cerevisiae cp3] pair was selected as the best strain which produced ethanol of 10.11% (w/v) or 12.81% (v/v) from 25% (w/v) glucose at $33^{\circ}C$ for 3 days with the residual sugar of 3.53% (w/v), viability of 62.65%, fermentation efficiency of 92.2%.