• Journal of Microbiology and Biotechnology
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• 제19권6호
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• pp.547-555
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• 2009

Nanoscopic changes in the cell surface morphology of the yeasts Saccharomyces cerevisiae (strain NCYC 1681) and Schizosaccharomyces pombe (strain DVPB 1354), due to their exposure to varying concentrations of hydrogen peroxide (oxidative stress), were investigated using an atomic force microscope (AFM). Increasing hydrogen peroxide concentration led to a decrease in cell viabilities and mean cell volumes, and an increase in the surface roughness of the yeasts. In addition, AFM studies revealed that oxidative stress caused cell compression in both S. cerevisiae and Schiz. pombe cells and an increase in the number of aged yeasts. These results confirmed the importance and usefulness of AFM in investigating the morphology of stressed microbial cells at the nanoscale. The results also provided novel information on the relative oxidative stress tolerance of S. cerevisiae and Schizo pombe.

• Journal of Microbiology and Biotechnology
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• 제17권2호
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• pp.297-304
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• 2007

The effect of yeast propagated at different aeration conditions on yeast physiology, fermentation ability, and beer quality was investigated using three strains of Saccharomyces cerevisiae. It was shown that yeast cells grown under continuous aeration conditions during propagation were almost two times higher as compared with discontinuous aeration conditions. The maximum of cell growth of all samples reached between 36 hand 48 h. The concentration of trehalose was increased under continuous aerated yeasts, whereas glycogen was decreased. It was also observed that the concentration of glycogen and trehalose in yeast cells had no direct effect on subsequent fermentation ability. The effect of yeast propagated under different aeration conditions on subsequent fermentation ability was different from yeast strains, in which the influence will be most pronounced at the first fermentation. Later, the yeasts might regain its original characteristics in the following fermentations. Generally, continuously propagated yeast had a positive effect on beer quality in subsequent fermentation. Hence, the concentration of aroma compounds obtained with yeast propagated under 6 1/h for 48 h aeration was lower than those grown under other aeration conditions in the bottom yeasts; in particular, the amounts of phenylethyl alcohol, ester, and fatty acids were decreased.

• 동의생리병리학회지
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• 제29권1호
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• pp.101-113
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• 2015

Application of herbal medicines as natural preservatives has been increased because of its low toxicity or side effect, compared to artificial preservatives. In this study, papers and patents researching anti-microbial activity of herbal medicine were collected and analyzed by the year of publishment, species of bacteria, fungi, or yeasts, and herbal medicines used. After early 2000's, the number of paper publishment has been decreased, while that of patent registration has been increased up to early 2010's. Most studied species were Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa, as gram-positive or gram-negative bacteria, and Candida albicans and Aspergillus niger as fungi. The bark of Cinnamomum cassia (L.) J. Presl was most frequently studies herbal medicine, followed by the roots of Scutellaria baicalensis Georgi and Sophora flavescens Ait. This study demonstrates that herbal medicines can be used as natural preservatives against diverse species of bacteria, fungi, or yeasts with their wide-ranged anti-microbial activities.

• Applied Biological Chemistry
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• 제30권1호
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• pp.31-39
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• 1987

영지(靈芝(Ganoderma lucidum(Fr.) Karst)) 추출물이 효모(Saccharomyces cerevisiae)의 증식과 생리에 미치는 영향을 검토하기 위하여 재배별 영지추출물을 각각 0, 0.1, 0.5, 1.0% 첨가한 Hayduck 액 배지에 효모를 접종하여 5일간 $30^{\circ}C$에서 발효시키면서 $CO_2$ 발생량, 균체생산, alcohol 발효 등을 조사하였다. 발효과정중 효모의 $CO_2$ 발생량은 발효 120시간 경과후 영지추출물 첨가구에서 모두 대조구보다 증가하였으며 이들 중 병재배 영지추출물 1.0% 첨가구에서 $CO_2$발생량이 가장 많았다. 발효과정중 효모의 세포수는 영지추출물 첨가구의 경우 모두 대조구보다 증가하였으며 병재배 영지추출물 첨가구가 원목영지추출물 및 야생영지추출물보다 세포수가 많았다. 효모의 건조균체량은 pot 0.5%구(區)>Pot 1.0%구(區) wild 1.0%구(區)>wood 1.0%구(區)>wood 0.5%구(區)>wild 0.5% 구(區)>wild 0.1% 구(區)>Pot 0.1% 구(區)> wood 0. 1% 구(區)>대조구의 순서로 증가하였으며 병재배영지추출물 첨가구는 원목재배나 야생영지추출물 첨가구보다 많았다. 각 처리구의 alcohol 함량은 발효 72시간의 경우 영지추출물 첨가구는 모두 대조구보다 3배 이상으로 많았으나 120시간 발효 후에는 큰 차이가 없었다. 발효과정중 효모의 당소비율과 발효율은 발효초기에 영지추출물 첨가구가 대조구보다 현저히 높았으나, 그 후 시간이 경과함에 따라 비슷하게 나타났다.

• Food Science and Biotechnology
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• 제17권4호
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• pp.739-744
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• 2008

The method of yeast propagation has an influence on yeast physiology, fermentation ability, flocculation rate, and taste stability of beer. In order to find optimal conditions for propagation, several parameters were investigated in combinations. The bottom brewing yeast grown at $10^{\circ}C$ indicated that a higher flocculation capacity during the $1^{st}$ fermentation. However, the taste stability and the aroma profile were not affected by parameters of propagation investigated. The beer quality was rather affected by storage duration. In addition, a correlation between tasting and chemiluminescence was found at the beer, which was produced using bottom brewing yeast. The propagation at $10-25^{\circ}C$ with addition of zinc ion indicated the best condition to improve fermentation ability, flocculation rate, and filterability for bottom brewing yeast, whereas the propagation at $30^{\circ}C$ with addition of zinc ion showed the best condition to increase fermentation ability for top brewing yeasts.