31. Implementation of liquid chromatography coupled to thermal lens spectrometry (HPLC-TLC) in studies of yeats' role in formation of stable pigments in Pinot Noir winesBranka Mozetič Vodopivec, Jelena Topić, Lorena Butinar, Natka Ćurko, Karin Kovačević Ganić, Dorota Korte, Mladen Franko, 2019, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: thermal lens spectrometry, pigments, Pinot Noir wines
Objavljeno v RUNG: 16.07.2019; Ogledov: 3503; Prenosov: 0
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33. Elided Clausal Conjunction Is Not the Only Source of Closest‐Conjunct Agreement: A Picture‐Matching StudyBoban Arsenijević, Jana Willer-Gold, Nadira Aljović, Nermina Čordalija, Marijana Kresić, Nedžad Leko, Frane Malenica, Franc Marušič, Tanja Milićev, Nataša Milićević, Petra Mišmaš, Ivana Mitić, Anita Peti-Stantić, Branimir Stanković, Jelena Tušek, Andrew Nevins, 2019, izvirni znanstveni članek Opis: A recurring hypothesis about the agreement phenomena generalized as closest‐conjunct agreement takes this pattern to result from reduced clausal conjunction, simply displaying the agreement of the verb with the nonconjoined subject of the clause whose content survives ellipsis (Aoun, Benmamoun & Sportiche 1994, 1999; see also Wilder 1997). Closest‐conjunct agreement is the dominant agreement pattern in the South Slavic languages Slovenian and Bosnian/Croatian/Serbian. A natural question is whether closest‐conjunct agreement in these varieties may indeed be analyzed as entirely derived from conjunction reduction. In this article, we report on two experiments conducted to test this. The results reject the hypothesis as far as these languages are concerned, thereby upholding the relevance of models developed to account for closest‐conjunct agreement within theories of agreement.
Ključne besede: Conjunct agreement, Clausal conjunction, Experimental syntax
Objavljeno v RUNG: 08.04.2019; Ogledov: 12045; Prenosov: 136
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35. Characterization of lactic bacteria for biogenic amine formationJelena Topic, Lorena Butinar, Martina Bergant Marušič, Dorota Korte, Branka Mozetič Vodopivec, 2018, samostojni znanstveni sestavek ali poglavje v monografski publikaciji Opis: Biogenic amines are compounds present in many different foods and beverages (wine, beer, dairy products, fermented vegetables and soy products, fish, etc.). Their presence in foodstuff is a result of a microbial action during storage and ageing. The most important are histamine, tryptamine, β-phenylethylamine and tryptamine, which can induce undesirable physiological effects in humans. They are formed through decarboxylation of corresponding amino acids, through the action of enzymes. Consumption of food containing biogenic amines can lead to food poisoning such as histamine poisoning. Histamine, the most studied biogenic amine, is known to cause headaches, oedema, vomiting, etc. [1]–[4]. Monitoring of the content of biogenic amines in foods is of concern for public health in their relation to the food safety, food spoilage and food intolerance. Because microorganisms are used in food productions as starters and biopreservers, characterization of microorganisms for their ability to produce biogenic amines is equally important. Lactic acid bacteria are often used as biopreservers as they can produce antimicrobial metabolites and antifungal peptides. Some strains can also produce undesirable biogenic amines [5]. In order to use lactic acid bacteria as starters or biopreservers, the selection of strains that would not produce biogenic amines is necessary.
When considering studies of biogenic amines in foods, focus should be on developing new or improving analysis methods for biogenic amines detection. Secondly, the connections between microorganisms capable of producing biogenic amines and the content of biogenic amines in foods should be investigated [3]. The most widely technique used for quantification of biogenic amines in foodstuff is liquid chromatography, Alternatively to chromatographic techniques, other techniques such as enzymatic biosensors, ELISA and flow-injection analysis have also been employed. Sensors are interesting due to the fact that they do not require special instrumentations, and there is no need for sample clean-up and derivatization, which are the main drawback of chromatographic methods [4]. Detection of biogenic amines producing lactic bacteria is important due to the concerns for public health and there is a need for the early and rapid detection of such microorganisms. Most of the methods that are used for screening involved the measurement of amino acid-decarboxylase activity, although there were been some methods reported that used differential media and pH indicators. Nowadays, molecular methods are replacing culture methods. Molecular approaches are used to determine the presence or absence of genes responsible for biogenic amines formation. The main advantages of DNA hybridization and PCR methods are speed, simplicity, sensitivity and specificity as they allow detection of targeted genes. Culture independent methods which are based on PCR techniques are now regarded as most suitable methods for screening isolates [5].
[1] A. R. Shalaby, “Significance of biogenic amines to food safety and human health,” Food Res. Int., vol. 29, no. 7, pp. 675–690, Oct. 1996.
[2] J. M. Landete, S. Ferrer, and I. Pardo, “Biogenic amine production by lactic acid bacteria, acetic bacteria and yeast isolated from wine,” Food Control, vol. 18, pp. 1569–1574, 2007.
[3] F. B. Erim, “Recent analytical approaches to the analysis of biogenic amines in food samples,” TrAC - Trends in Analytical Chemistry, vol. 52. pp. 239–247, 2013.
[4] J. L. Ordóñez, A. M. Troncoso, M. D. C. García-Parrilla, and R. M. Callejón, “Recent trends in the determination of biogenic amines in fermented beverages – A review,” Analytica Chimica Acta, vol. 939. pp. 10–25, 2016.
[5] R. M. Elsanhoty and M. F. Ramadan, “Genetic screening of biogenic amines production capacity from some lactic acid bacteria strains,” Food Control, vol. 68, pp. 220–228, Oct. 2016.
Ključne besede: lactic bacteria, biogenic amines
Objavljeno v RUNG: 13.12.2018; Ogledov: 3490; Prenosov: 0
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38. Simple and fast HPLC-DAD method for determination of HCDC activity and formation of vinylphenol in Saccharomyces and non-Saccharomyces yeastJelena Topič, Lorena Butinar, Dorota Korte, Branka Mozetič Vodopivec, objavljeni povzetek znanstvenega prispevka na konferenci Opis: Conventionally, alcoholic fermentation in the production of wine is performed by yeast species Saccharomyces cerevisiae. There are numerous starters available, however due to the growing demand for wines with specific characteristics, other Saccharomyces and non-Saccharomyces species are being investigated for potential use as starters. [1]. Yeast selection has involved the development of techniques for detecting strains that might improve wines in terms of aroma, structure, colour and other technological properties [2]. Colour of the wine can be affected as some metabolites produced by yeast during fermentation may react with grape anthocyanins to produce highly stable pyranoanthocyanins. For the facilitation of formation of vinylphenolic pyranoanthocyanins, yeast strains with high hydroxycinnamate decarboxylase activity are used (HCDC). The mechanism of reaction is decarboxylation of hydroxycinnamic acids and formation of vinylphenols that condense with grape anthocyanins and form stabile vinyphenolic pyranoanthocyanin adducts [3]. It has been demonstrated that some non-Saccharomyces strains (Pichia guillermondii, Schizosaccharomyces pombe) have positive HCDC activity and they can produce vinylphenolic pyranoanthocyanins in higher concentrations than S. cerevisiae. A simple way of determining whether the yeast strain has HCDC activity or not, is the use of fermentation media with the addition of hydroxycinnamic acids, such as p-coumaric acid. The degradation of p-coumaric acid and transformation into 4-vinylphenol (and possibly in 4-ethylphenol) can be checked by LC-DAD. Most of the published data has been done on smaller number of strains.
The goal of our work was to develop simple method for the screening of Slovenian in-house yeast collection, comprising of native isolates that mostly originated from Vipava valley and Karst region, and therefore try to determine strains with high HCDC activity. These strains can be used for wine fermentations in order to produce more stable pyranoanthocyanins; which is especially important in wines that has less anthocyanin concentration already from the grape, such as Pinot Noir.
103 different yeast strains belonging to 28 species were selected for the assessment of HCDC activity. In some cases the difference in p-coumaric acid metabolism rate between two strains exceeded 90%. All tested S. paradoxus strains showed higher than 40% degradation rate of p-coumaric acid. HCDC activity of S. cerevisiae strains which is the species most commonly used in fermentation, varied between 5.1 and 66.1%. The commercial strains tested, FPC and EC118 showed 43.9 and 21.5% conversion rate, respectively. It was observed that some native strains had higher HCDC activity than commercial tested ones. Three strains produced vinylphenol in concentration higher than 50 ppm, two of them being P. guillermondii and another strain being S. paradoxus (Sut85). In general strain with high HCDC activity also produced high concentration of 4-vinylphenol.
The results showed that HCDC activity is highly strain dependent, which correlates with the literature data available. The proposed method is very simple and does not require special sample preparation prior to HPLC analysis. Furthermore, the proposed fermentations in deep-well microtiter plates allow the screening of high number of strains. The method could be used for routine screening, to determine which strain has high HCDC activity and produces high concentration of vinylphenols and can therefore be used in future for determination of strains ability to synthesize vinylphenolic pyranoanthocyanins.
Ključne besede: yeast, hydroxycinnamate decarboxylase, 4-vinylphenol
Objavljeno v RUNG: 18.06.2018; Ogledov: 4060; Prenosov: 0
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