STUDY OF MICROBIAL ADHESION TO SOLVENTS AND RESISTANCE OF aboriginal STRAINS Saccharomyces cerevisiae to different pH values
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Из 180 штаммов дрожжей Saccharomyces cerevisiae, выделенных из различных растительных субстратов, по предварительно изученным технологическим параметрам, такие как скорость сбраживания и органолептическим показателям ферментированных фруктовых соков отобрано 15 штаммов. Отобранные штаммы изучены на способность к выживанию при низких значениях рН и обладающих высокой микробной адгезией к органическим растворителям. Семь штаммов дрожжей (BB-5, BB-32, VSs-2, Az- 12, Al-06, Gl-8, Ab-13) показали наиболее высокий процент по микробной адгезии к органическим растворителям. Самая высокая толерантность к низким значениям pH=3 с индексом роста> 90% обнаружена у 4 штаммов, идентифицированных как Saccharomyces cerevisiae Al-06 (из винограда), Saccharomyces cerevisiae Gl -8 (из сока сахарного сарго), Saccharomyces cerevisiae BB-5 (из сока вишни) и Saccharomyces cerevisiae Az- 12 (из гранатового сока). Эти штаммы демонстрируют лучшие характеристики, а один из протестированных штаммов Saccharomyces cerevisiae Az- 12 потенциально может использоваться для производства пищевых добавок, функциональных пищевых напитков, а также в качестве пробиотика для терапевтических целей. From 180 strains of Saccharomyces cerevisiae yeast isolated from various plant substrates, 15 strains were selected according to previously studied technological parameters such as digestion rate and organoleptic characteristics of fermented fruit juices. The selected strains were tested for their ability to survive at low pH values and having high microbial adhesion to organic solvents. Seven strains (BB-5, BB-32, VSs-2, Az-12, Al-06, Gl-8, Ab-13) showed a higher percentage of microbial adhesion to organic solvents. The highest tolerance to low pH=3 with a growth index >90% was found in 4 strains identified as Saccharomyces cerevisiae Al-06 (from grapes), Saccharomyces cerevisiae Gl-8 (from sugar sargo juice), Saccharomyces cerevisiae BB-5 (from cherry juice) and Saccharomyces cerevisiae Az-12 (from pomegranate juice). These strains show the best characteristics, and one of the tested strains of Saccharomyces cerevisiae Az-12 has the potential to be used for the production of nutritional supplements, functional food drinks, and also as a probiotic for therapeutic purposes.Cells of the yeast Saccharomyces cerevisiae are transformable by DNA under non‐artificial conditions
Transformants of bakers' yeast (Saccharomyces cerevisiae) can be generated when non-growing cells metabolize sugars (without additional nutrients) in the presence of plasmid DNA. These results suggest that there is a mechanism by which DNA can naturally be taken up by the yeast cell. Natural transformation does not take place in common complete or minimal yeast culture media such as YPD and YNB. The starvation conditions used in our experiments thus seem to be an important prerequisite for such transformation events. Copyright © 2000 John Wiley & Sons, Ltd.
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Saccharomyces diastaticus KCTC 1804 균주와 Saccharomyces cerevisiae KOY-1 균주를 이용하여 전분분해활성과 알코올 발효능을 동시에 가지는 효모융합체를 개발하였다. Saccharomyces cerevisiae KOY-1 균주의 단수체 유도를 통하여 Saccharomyces cerevisiae KH-12 균주를 획득하였다. EMS를 사용한 돌연변이 유발을 통하여 Saccharomyces cerevisiae KH-12 균주의 Met 영양요구성 변이주를 획득하였다. Lyticase 처리로 Saccharomyces cerevisiae KOY-1 Met?), Saccharomyces diastaticus KCTC 1804(Trp?) 균주의 원형질체 형성률은 각각 90.5%, 97.7%로 관찰되었다. 원형질체 융합은 polyethylene glycol 4,000을 이용하여 실시하였고, 이때 원형질체 융합율은 1.79 × 10-4으로 관찰되었다. 원형질체융합과정을 통해 총 1,000주의 융합체를 획득하였고, 획득한 융합체의 전분분해능과 알코올발효능을 비교하여 최종적으로 전분배지 YPS24에서 알코올생성능이 가장 우수한 효모융합체인 FA 776을 최종 선발하였다. 최종 선발된 효모융합체 FA 776은 10세대 계대배양 후의 revertent 복귀율이 4.64%로 유전적 안정성을 확인하였으며, 효모융합체의 total DNA 함량을 비교한 결과, Saccharomyces cerevisiae 균주로부터 분리된 단수체 효모 KH-12는 26.56 fg/cll, Saccharomyces diastaticus KCTC 1804 균주는 25.40 fg/cell이었고, 이들을 사용해서 얻어진 융합체 FA 776의 DNA 함량은 42.67 fg/cell이었다. 전분배지 YPS24 배지에서 60시간 발효하였을때 Saccharomyces cerevisiae KOY-1 균주는 알코올 생성하지 못하였지만 효모융합체 FA 776은 13 mg/mL의 알코올을 생성하였다. 이는 전분이용성 효모인 Saccharomyces diastaticus KCTC 1804 균주에 비해 1.86배나 향상된 알코올 발효능을 나타냈다.
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Lin's copper sulphate medium for the detection of non-Saccharomyces wild yeast was modified, mainly by reducing the concentration of copper sulphate, with the aim of producing a medium that could detect a wide range of both non-Saccharomyces and Saccharomyces wild yeast. The performance of the resultant MYGP + Cu medium was compared to that of crystal violet and lysine media using pure cultures of wild yeast, pitching yeast and brewery samples. The growth of the pitching yeasts examined was suppressed more in MYGP + Cu than in crystal violet and the 4 ale yeasts were more susceptible to copper inhibition than the 3 lager yeasts. Neither MYGP + Cu nor crystal violet could detect all the wild Saccharomyces species tested but the proportion detected by each was similar. Twenty-seven out of 28 non-Saccharomyces wild yeasts tested could be detected in MYGP + Cu. When brewery samples were examined, the detection rate by MYGP + Cu compared favourably with that by a combination of crystal violet and lysine. MYGP + Cu is particularly suited to the monitoring of the production of cask-conditioned ales.
Crystal violet
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One of the key feature of prions is the ability to be stable in two alternative conformations. Besides the intensively studied mammalian prions, there are also prion proteins present in the yeast Saccharomyces cerevisiae. Research in this field has lead to opposite hypotheses that explain the sense of presence of [PSI+] prion in yeast cells. Some authors postulate e of role of the prions in the evolution of S. cerevisiae, whereas other investigators point out the negative influence of these particles upon the yeast physiology. In recent years, yeast prions are used for anti-prion drug screening, because of common features with mammalian prions. This work presents the most intensively studied fields of the research carried out on [PSI+] prion in yeast.
Prion Proteins
Fungal prion
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The use of non-Saccharomyces yeast species generally involves sequential or co-inoculation of a Saccharomyces cerevisiae strain to complete fermentation. While most studies have focused on characterising the impact that S. cerevisiae has on the growth and metabolic activity of these non-Saccharomyces species, microbial interactions work reciprocally. Antagonism or competition of non-Saccharomyces species against S. cerevisiae has been shown to impact subsequent fermentation performance. To date, it remains unclear whether these negative interactions are strain specific. Hence, characterisation of strain-specific responses to co-inoculation would enable the identification of specific S. cerevisiae strain/non-Saccharomyces combinations that minimise the negative impacts of sequential fermentation on fermentation performance. The competitive fitness response of 93 S. cerevisiae strains to several non-Saccharomyces species was simultaneously investigated using a barcoded library to address this knowledge gap. Strain-specific fitness differences were observed across non-Saccharomyces treatments. Results obtained from experiments using selected S. cerevisiae strains sequentially inoculated after Metschnikowia pulcherrima and Torulaspora delbrueckii were consistent with the competitive barcoded library observations. The results presented in this study indicate that strain selection will influence fermentation performance when using non-Saccharomyces species, therefore, appropriate strain/yeast combinations are required to optimise fermentation.
Torulaspora delbrueckii
Strain (injury)
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Ethyl methanesulfonate
Methyl methanesulfonate
Strain (injury)
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The Saccharomyces sp. CID1 isolate (CBS 8614) and several other Saccharomyces sensu stricto yeasts were analysed for their mitochondrial and nuclear genes. The data show that Saccharomyces sp. CID1, found so far only in one location in Europe, is a natural hybrid between three different Saccharomyces yeast species. Two of them, Saccharomyces cerevisiae-like and Saccharomyces bayanus-like, are ubiquitous and contributed parts of the nuclear genome; the third, Saccharomyces sp. IFO 1802-like, which has been found only in Japan, contributed the mitochondrial DNA molecule. These data suggest that the yeast cell is able to accommodate, express and propagate genetic material that originates from different species, and the very existence of the resulting natural hybrids indicates that such hybrids are well adapted to their habitats.
Nuclear gene
Nuclear DNA
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The paper describes the use of crystal-violet and lysine containing media to detect yeast infection in brewing and to classify it. The crystal-violet containing medium helps to separate brewing yeast Saccharomyces cerevisiae and Saccharomyces carlsbergensis from wild yeast of the Saccharomyces genus, whereas the lysine containing medium--from wild yeast of the genera Candida, Debaryomyces, Brethanomyces, Pichia. The test has been used both on museum cultures and on yeast isolated from beer and non-alcoholic beverages.
Crystal violet
Pichia
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Treatment of yeast Saccharomyces cerevisiae with alpha-pheromone has been reported to lead to massive apoptosis of cells finding no conjugation partner [Severin FF, Hyman AA. Pheromone induces programmed cell death in S. cerevisiae. Curr Biol 2002;12:R233-5]. We report here that this effect is not common in yeast. Using different yeast strains, we demonstrate that identical treatment results in a low mortality even after prolonged treatment with the pheromone. These findings are followed by a general discussion of the biological relevance of apoptosis in yeast.
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