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Developments in yeast genetics, biochemistry, physiology and process engineering provided bases of rapid development in modern biotechnology. Elaboration of the recombinant DNA technique is far the most important milestone in this field. Other molecular genetic techniques, as molecular genotyping of yeast strains proved also very beneficial in yeast fermentation technologies. Saccharomyces cerevisiaeis the most exploited eukaryotic microorganism in biotechnology but non-Saccharomycesspecies are becoming more and more important in the production of perfectly translated heterologous proteins.

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Roots of classical yeast genetics go back to the early work of Lindegreen in the 1930s, who studied thallism, sporulation and inheritance of wine yeast strains belonging to S. cerevisiae. Consequent mutation and hybridization of heterothallic S. cerevisae strains resulted in the discovery of life cycle and mating type system, as well as construction of the genetic map. Elaboration of induced mutation and controlled hybridization of yeast strains opened up new possibilities for the genetic analysis of technologically important properties and for the production of improved industrial strains, but a big drawback was the widely different genetic properties of laboratory and industrial yeast strains. Genetic analysis and mapping of industrial strains were generally hindered because of homothallism, poor sporulation and/or low spore viability of brewing and wine yeast strains [1, 2]. In spite of this, there are a few examples of the application of sexual hybridization in the study of genetic control of important technological properties, e.g. sugar utilization, flocculation and flavor production in brewing yeast strains [3] or in the improvement of ethanol producing S. cerevisiae strains [4]. Rare mating and application of karyogamy deficient (kar) mutants also proved useful in strain improvement [5].Importance of yeasts in biotechnology is enormous. This includes food and beverage fermentation processes where a wide range of yeast species are playing role, but S. cerevisiae is undoubtedly the most important species among them. New biotechnology is aiming to improve these technologies, but besides this, a completely new area of yeast utilization has been emerged, especially in the pharmaceutical and medical areas. Without decreasing the importance of S. cerevisiae, numerous other yeast species, e.g. Kluyveromyces lactis, Hansenula polymorpha, Pichia pastoris, Schizosaccharomyces pombe and Yarrowia lipolytica have gained increasing potentialities in the modern fermentation biotechnology [6].Developments in yeast genetics, biochemistry, physiology and process engineering provided bases of rapid development in modern biotechnology, but elaboration of the recombinant DNA technique is far the most important milestone in this field. Other molecular genetic techniques, as molecular genotyping of yeast strains proved also very beneficial in yeast fermentation technologies, because dynamics of both the natural and inoculated yeast biota could be followed by these versatile DNA-based techniques.

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Absztrakt

A biztonságos élelmiszerek előállítása szempontjából kulcsfontosságú az élelmiszerrel terjedő patogén baktériumok kimutatása és azonosítása. A hagyományos, tenyésztésen alapuló diagnosztikai eljárásokat egyre inkább felváltják vagy kiegészítik a nukleinsav-alapú, a genom speciális (elsősorban virulencia) génjeinek kimutatását célzó molekuláris technikák. A rutin élelmiszer-mikrobiológiai vizsgáló laboratóriumok leggyakrabban nemzetközileg validált DNS-amplifikációs, elsősorban valós idejű polimeráz láncreakció alapú módszereket alkalmaznak, amelyek a vizsgálati idő jelentős lerövidítése mellett lényegesen javítják a módszerek teljesítési jellemzőit (például érzékenység, specifikusság) is. A polimeráz láncreakció alapú módszereknek rutindiagnosztikai célú alkalmazása azonban az előnyök mellett számos hátránnyal is jár, amelyek között említendő a készülékek és a reagensek magas költsége, valamint a laboratóriumi környezetnek a reakciótermékekkel való kontaminálási kockázata, ami elkülönített laboratóriumi rendszert igényel. Manapság az ilyen laboratóriumi rendszerek miniatürizálása és hordozhatóvá tétele is fontos fejlesztési irány. A Lab-on-a-chip eszközökben több ilyen laboratóriumi műveletet lehet megvalósítani egy kis méretű eszközön, a standard eljárásokhoz hasonló pontossággal és megbízhatósággal. Ezen miniatürizált eszközök nagy előnye az egyszerű – sokszor automatizált – kezelhetőség, kis méret, hordozhatóság és sterilitás, ami az egyszeri használatból adódik. Ilyen miniatürizált gyorsdiagnosztikai eszközök kutatása és fejlesztése folyik a világ vezető kutatóhelyein, például különböző minta-előkészítési és DNS-amplifikációs módszerek miniatürizálásával. A szerzők is ezt a célt tűzték ki kutatásaikban: olyan miniatürizált mikrofluidikai eszközök fejlesztését, amelyek alkalmasak élelmiszer-biztonsági jelentőségű baktériumok molekuláris detektálására. Orv. Hetil., 2015, 156(51), 2082–2088.

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Scanning and transmission electron microscopic studies revealed the presence of slime-like, amorphous material on the surface of Schizosaccahromyces pombe RIVE 4-2-1 cells, independently, whether they were in flocculated or in non-flocculated state. Close contact of the adjacent cells via the merging outermost cell wall layers was found, however, only in the case of floc formation, which was induced by cultivating the cells in the presence of 6% (v/v) ethanol. Irreversible loss of the flocculation ability of the cells by treatment with proteinases suggests that proteinaceous cell surface molecules as lectins contribute to the cell-to-cell interaction during flocculation. Both proteinase K and pronase treatments removed a distinct outer layer of the cell wall, which indicated that the protein moieties of the phosphogalactomannan outer surface layer has a crucial role in the maintenance of cell wall integrity. In the case of lysing enzyme treatment the removal of the outermost layer was also observed as the first step of the cell wall digestion, while driselase treatment resulted in almost complete digestion of the cell wall.

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Sulphur plays an important role in yeasts, especially in the biosynthesis of methionine and cysteine. The inorganic sulphur source, sulphate, is taken up by the cells via the sulphate-permease(s). After its transport, it is activated and subsequently reduced to sulphide or serves as a donor for sulphurylation reactions. Selenate anion (SeO4 2-), which has the same metabolic pathway as sulphate, is toxic for the cells of Schizosaccharomyces pombe. We isolated selenate resistant mutants which cannot utilize sulphate, therefore they need organic sulphur source for growth. One of the selenate resistant mutants was successively transformed with S. pombe genomic libraries and the gene complementing the selenate resistance was identified as that of coding for the ATP-sulphurylase enzyme.

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Abstract

The aim of our research was to study the water and ethanol extractable polyphenols of stinging nettle (Urtica dioica L.) harvested in different seasons and to determine their antimicrobial activity against certain human pathogenic and food spoiling bacteria and yeasts.

Our results indicate that the spring leaf extracts had higher polyphenol contents than the root one; however, close to the end of the vegetation period these values decreased considerably in both leaves and roots. Detection and quantification of the most abundant phenolic compounds in the spring extracts by HPLC revealed the occurrence of 12 different phenol carboxylic acids and flavonoids. Flavonoid compounds were more abundant than phenol carboxylic acids in the leaves; however, their proportion was equal in the case of the roots. Nettle leaf extracts had remarkable antimicrobial activity, the spring extracts were more efficient than the autumn ones. Escherichia coli and Staphylococcus aureus were sensitive to every leaf extract, while Listeria monocytogenes and Pseudomonas aeruginosa had reduced but remarkable sensitivity patterns. Among the yeasts, Candida glabrata was strongly inhibited by the aqueous leaf extracts. Most of the strains were insensitive to the root extracts, although Enterococcus faecalis was inhibited by the root and not the leaf extracts.

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