• 분석과학
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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

Glucose와 lactose를 이용한 알콜발효에서 Sacchar-omyces cerevisine STV89와 Kluyveromyces fragilis CBS397의 에탄올 내성에 대한 발효온도의 영향에 관한 연구를 수행하였다. 최대 비성장 속도와 에탄올 생성 속도는 발효온도에 따라 35$^{\circ}C$까지 증가하였으나 최대 cell 농도와 에탄올 농도는 발효온도 증가에 따라 감소하였다. Cell viability도 역시 발효온도가 낮을수록 향상되었다. 따라서 수행한 실험조건에서 효모의 에탄올 내성은 $25^{\circ}C$에서 가장 우수하였다. 균주의 비교에서 에탄올에 대한 내성이 S. cerevisiae가 K.fragilis보다 동일한 실험조건에서는 더 우수하였으며, 탄소원의 종류에 대한 비교에서 K. fragilis의 에탄올에 할 때보다 더 우수하였다.

• 한국식품과학회지
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• 제33권2호
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• pp.205-208
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• 2001

맥주 공장 부산물인 맥주효모 슬러리의 쓴맛을 제거하기 위하여 가성소다 액을 이용한 세척 시험을 하였다. 효모 슬러리를 묽은 가성소다 액에 침지시키고 세척함에 따라 쓴맛이 감소하였는데, 가성소다 액의 농도를 0.05%(w/v)에서 0.25%(w/v)로 단계적으로 증가시킴에 따라 맥주 효모의 쓴맛 정도(bitterness unit)가 45 BU에서 3.0 BU까지 낮아진 반면 효모가 폐사되는 단점이 나타났다. 쓴맛 제거 정도와 세척 효모의 생존율을 동시에 고려할 때 $0.07{\sim}0.1%$(w/v) pH로는 $9.5{\sim}10.5$인 가성소다 액에 효모 슬러리를 넣고 $10{\sim}20$분 방치한 다음 0.85%(w/v) NaCl 용액으로 세척하는 것이 가장 좋은 것으로 나타났다. 세척된 효모 슬러리는 세척 전보다 백색(whiteness)이 증가되었으며 황색(yellowness)은 감소하였다. 이외에도 알코올 용액을 사용하여 세척해도 우수한 쓴맛제거 효과를 얻을 수 있었다.

• 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

본 시험은 면역계에서 중요한 역할을 담당하는 세포가운데 하나인 대식세포(Raw 264.7)를 게르마늄 강화 효모가 활성화시키는지 여부를 알아보기 위하여 대식세포의 배양액으로부터 NO와 $TNF-{\alpha}$의 생성을 in vitro 상에서 알아보고 iNOS의 발현 정도를 확인하고자 실시하였으며, 그 결과는 다음과 같다. 게르마늄 강화 효모 처리 후 세포 생존율(%)과 NO 생성량은 $10\;{\mu}g/ml$의 처리 농도에서 유의적으로 증가하였다(p < 0.05). 또한 NO 생성을 매개하는 iNOS의 발현 역시 $10\;{\mu}g/ml$의 농도에서 증가한 것으로 나타났다. 면역 및 항암 조절 인자로 알려진 $TNF-{\alpha}$의 생성 역시 농도 의존적으로 증가하였으며, $10\;{\mu}g/ml$의 처리 농도에서 유의적으로 증가하였다(p < 0.05). 이는 게르마늄 강화 효모가 항암 및 면역 증진 기능과 관련이 있는 $TNF-{\alpha}$ 분비를 촉진시키는데 영향을 준 것으로 사료된다. 따라서 본 시험 모델에서 게르마늄 강화 효모는 iNOS 발현을 조절하여 NO 및 $TNF-{\alpha}$의 생성을 매개하여 면역조절 기능에 도움을 줄 것으로 사료된다. 이것은 면역기능에 있어서 중요한 역할을 하는 대식세포를 활성화시켜 면역력을 활성화시키므로 세포성 면역의 활성화를 도모하고 손상된 면역 체계의 정상화에 영향을 주어 면역 강화 및 항암 예방 기능성 신소재로의 가능성을 지니는 것으로 사료된다.

• 미생물학회지
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• 제37권4호
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• pp.312-316
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• 2001

에탄올 발효능이 우수한 Saccharomyces에 속하는 4 균주를 가지고 여러 조합의 mating-pair 또는 fusion-pair를 만들고 이들 pair들로부터 만들어진 hybrid주들의 에탄올 생성능과 생존능을 통계적으로 분석한 결과, 에탄올 생성능에서는 차이가 없었으나, 생존능의 경우는 [S. kluveri $khl{\times}S.$ cerevisiae cp3]의 균주조합이 가장 우수한 hybrid를 낼 수 있는 것으로 나타났다. 실제로 에탄올 생성능과 잔당, 효율, 생존능에서 두루 우수한 균주는 [S. kluveri $khl{\times}S$ cerevisiae cp3] 조합에서 얻어진 융합주 clone No. 3가 에탄올 생성능 10.11%(w/v) 또는 12.81%(v/v), 잔당 3.53%(w/v), 생존능 62.65%, 발효 효율 92.2%로서 가장 발효능과 생존능이 우수한 균주로 선정되었다.