2 résultat(s) recherche sur le tag 'yeast'    

Activité Killer chez des levures isolées des sols du Nord-Est Algérien / Fatima-Zohra-Kenza Labbani  

Public ISBD Titre : Activité Killer chez des levures isolées des sols du Nord-Est Algérien : Purification, caractérisation et effet sur les souches de levures indésirables. Type de document : texte imprimé Auteurs : Fatima-Zohra-Kenza Labbani, Auteur ; Zahia Meraihi, Directeur de thèse Editeur : جامعة الإخوة منتوري قسنطينة Année de publication : 2015 Importance : 103 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais Biologie Tags : levures  isolement  Pichia kluyveri  toxine killer  biocontrôle  levures indésirables  Yeast  isolation  killer toxin  biocontrol  undesirable yeasts  ?????  ???  ?? ????  ?????? ?????  ????? ??? ????? ???? Index. décimale : 570 Sciences de la vie. Biologie Résumé : The general purpose of this thesis is to search for killer activity in yeast strains isolated from agricultural and forest soil in the region of Constantine for biotechnological applications.The isolation of yeasts allows to list 15 strains. The molecular taxonomy based on the sequences of D1/D2 domain of the 26S ribosomal ARN gene groups these isolates into 6 different species: Cryptococcus aerius, Hanseniaspora opuntiae, Hanseniaspora uvarum, Pichia kluyveri, Meyerozyma guilliermondii and Saccharomyces cerevisiae. Morphological, physiological and biochemical characteristics of the strains are in agreement with those cited in literature. Preliminary testing for killer activity reveals that only the strain L5 is able to produce killer activity. The killer strain is belonging to the species P. kluyveri. The crude killer protein produced by the strain P. kluyveri reveals that the toxin is active against food and beverage spoilage yeast strains belonging to the genera: Dekkera, Kluyveromyces, Pichia, Saccharomyces, Torulaspora, Wickerhamomyces and Zygosaccharomyces. The highest killer activity is obtained against the strain Dekkera bruxellensis DBVPG 6706. Both the heat shock (30 min at 100°C) and the enzymatic treatment with pronase demonstrate the complete loss of the initial killer activity of the toxin, and hence its proteinaceous nature is apparently confirmed. The active protein migrates as a single band in SDS-PAGE and has a molecular mass of 54 kDa. The purified killer toxin has an optimal pH between 4.0-4.5, while the optimal of temperature is 25°C.The determination of minimum inhibitory concentrations (MICs) shows that the purified killer protein has a high in vitro activity against D.bruxellensis (MICs from 64 000- to 256 000-fold lower than that exhibited by potassium metabisulphite) and Saccharomyces cerevisiae (MICs from 32 000- to 64 000-fold lower than potassium sorbate). No in vitro synergistic interactions (calculated by FIC index -Σ FIC) are observed when killer protein is used in combination with the active compounds : potassium metabisulphite, potassium sorbate, or ethanol. The killer protein exhibited a dose–response effect against D. bruxellensis and S. cerevisiae in a soft drink « Campari MIXX » (Milan, Italy) and pear juice « Santal » (Parma, Italy), respectively. The results of the present study suggest that the killer protein could be proposed as a novel food-grade compound useful for the control of food and beverage spoilage yeasts. Additionally, the purified killer protein maintains its killing action at least for 3 days against S. cerevisiae DBVPG 6500 inoculated in pear juice and for 10 days against D. bruxellensis DBVPG 6706 in soft drink. The results of the present study suggest that the killer protein produced by the strain P. kluyveri (L5) could be proposed as a novel natural agent for the biocontrole of beverage spoilage yeasts. Diplôme : Doctorat En ligne : ../theses/biologie/LAB6794.pdf Format de la ressource électronique : pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10026 Activité Killer chez des levures isolées des sols du Nord-Est Algérien : Purification, caractérisation et effet sur les souches de levures indésirables. [texte imprimé] / Fatima-Zohra-Kenza Labbani, Auteur ; Zahia Meraihi, Directeur de thèse . - [S.l.] : جامعة الإخوة منتوري قسنطينة, 2015 . - 103 f. ; 30 cm. 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais Biologie Tags : levures  isolement  Pichia kluyveri  toxine killer  biocontrôle  levures indésirables  Yeast  isolation  killer toxin  biocontrol  undesirable yeasts  ?????  ???  ?? ????  ?????? ?????  ????? ??? ????? ???? Index. décimale : 570 Sciences de la vie. Biologie Résumé : The general purpose of this thesis is to search for killer activity in yeast strains isolated from agricultural and forest soil in the region of Constantine for biotechnological applications.The isolation of yeasts allows to list 15 strains. The molecular taxonomy based on the sequences of D1/D2 domain of the 26S ribosomal ARN gene groups these isolates into 6 different species: Cryptococcus aerius, Hanseniaspora opuntiae, Hanseniaspora uvarum, Pichia kluyveri, Meyerozyma guilliermondii and Saccharomyces cerevisiae. Morphological, physiological and biochemical characteristics of the strains are in agreement with those cited in literature. Preliminary testing for killer activity reveals that only the strain L5 is able to produce killer activity. The killer strain is belonging to the species P. kluyveri. The crude killer protein produced by the strain P. kluyveri reveals that the toxin is active against food and beverage spoilage yeast strains belonging to the genera: Dekkera, Kluyveromyces, Pichia, Saccharomyces, Torulaspora, Wickerhamomyces and Zygosaccharomyces. The highest killer activity is obtained against the strain Dekkera bruxellensis DBVPG 6706. Both the heat shock (30 min at 100°C) and the enzymatic treatment with pronase demonstrate the complete loss of the initial killer activity of the toxin, and hence its proteinaceous nature is apparently confirmed. The active protein migrates as a single band in SDS-PAGE and has a molecular mass of 54 kDa. The purified killer toxin has an optimal pH between 4.0-4.5, while the optimal of temperature is 25°C.The determination of minimum inhibitory concentrations (MICs) shows that the purified killer protein has a high in vitro activity against D.bruxellensis (MICs from 64 000- to 256 000-fold lower than that exhibited by potassium metabisulphite) and Saccharomyces cerevisiae (MICs from 32 000- to 64 000-fold lower than potassium sorbate). No in vitro synergistic interactions (calculated by FIC index -Σ FIC) are observed when killer protein is used in combination with the active compounds : potassium metabisulphite, potassium sorbate, or ethanol. The killer protein exhibited a dose–response effect against D. bruxellensis and S. cerevisiae in a soft drink « Campari MIXX » (Milan, Italy) and pear juice « Santal » (Parma, Italy), respectively. The results of the present study suggest that the killer protein could be proposed as a novel food-grade compound useful for the control of food and beverage spoilage yeasts. Additionally, the purified killer protein maintains its killing action at least for 3 days against S. cerevisiae DBVPG 6500 inoculated in pear juice and for 10 days against D. bruxellensis DBVPG 6706 in soft drink. The results of the present study suggest that the killer protein produced by the strain P. kluyveri (L5) could be proposed as a novel natural agent for the biocontrole of beverage spoilage yeasts. Diplôme : Doctorat En ligne : ../theses/biologie/LAB6794.pdf Format de la ressource électronique : pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=10026

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
LAB/6794	LAB/6794	Thèse	Bibliothèque principale	Thèses	Disponible

Utilisation de l’huile essentielle de Citrus limon comme agent conservateur et aromatique dans la crème fraîche / Farida Kehal  

Public ISBD Titre : Utilisation de l’huile essentielle de Citrus limon comme agent conservateur et aromatique dans la crème fraîche Type de document : texte imprimé Auteurs : Farida Kehal, Auteur ; M Barkat, Directeur de thèse Editeur : constantine [Algérie] : Université Constantine 1 Année de publication : 2013 Importance : 104 f. Format : 30 cm. Note générale : 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais Nutrition, Alimentation et Technologies Agro-Alimentaires Tags : Crème fraîche  levures  bactéries  huile essentielle  écorce de citron  analyse sensorielle  Cream  yeast  bacteria  essential oil  lemon zest  sensory analysis  ?????? ???????  ??????? ??????????  ?????? ????????  ???? ???????  ???????? ?????? Index. décimale : 640 Industrie Alimentaire Résumé : This study was conducted in order to enhance the lemon peel (Citrus limon) by using their essential oil as a natural agent for preservation and aromatization in cream in order to diversify the types of existing cream on the market. This essential oil was extracted by hydroditillation, extraction yield was 0,89 ± 0,09%. The antioxidant activity of the extracted essential oil was studied by the DPPH° test, this free radical has been effectively reduced, compared to vitamin E. These results were confirmed by the test of β- carotene bleaching. The study of antimicrobial activity of essential oil of C. limon showed that two tested bacteria are resistant against the effectiveness of the oil, resulting in very high MICs (4% and > 8%). Regarding yeast strains isolated and tested Debaryomyces sp. and Rhodotorula sp., they have some sensitivity to the effect of essential oil, characterized by CMI respectively 0,25% and 0,5%. The other two strains Zygosaccharomyces sp1 and Zygosaccharomyces sp2, were resistant, their MICs are respectively in the order of 1% and > 4%. The various tests on the formulation of the added essential oil of C. limon creams were tested by developing three fresh creams with concentrations of 0,125%, 0,25%, 0,5%. Characteristics are conforms to standard. The results of physicochemical and microbiological analyzes prepared fresh cream after opening the package, show that the presence of the essential oil at low concentrations does not limit microbial spoilage. The evaluation of the oxidative stability by Schaal test indicates that the fresh cream with essential oil of C. limon are more resistant than the control opposite the forced oxidation. Sensory analysis show that the incorporation of essential oil in the cream, at concentrations of 0,125% and 0,25%, involves no significant difference (p > 0,05) in terms of flavoring, and make products which are classified in same order than the control. Only the rate of incorporation of the essential oil of 0,5% significantly downgraded the product compared to the control in the third row, which has led to changes in smell and flavor while the texture, color and taste are unchanged. The principal component analysis (PCA) showed a negative correlation (r = - 0,998) between the levels of incorporation of the essential oil and the aroma of raw milk, and a positive correlation (r = 0,956) with the color yellow. Diplôme : Magistère En ligne : ../theses/agronomie/KEH6360.pdf Format de la ressource électronique : pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=6352 Utilisation de l’huile essentielle de Citrus limon comme agent conservateur et aromatique dans la crème fraîche [texte imprimé] / Farida Kehal, Auteur ; M Barkat, Directeur de thèse . - constantine (Route ain el bey, Algérie) : Université Constantine 1, 2013 . - 104 f. ; 30 cm. 2 copies imprimées disponibles Langues : Français (fre) Catégories : Français - Anglais Nutrition, Alimentation et Technologies Agro-Alimentaires Tags : Crème fraîche  levures  bactéries  huile essentielle  écorce de citron  analyse sensorielle  Cream  yeast  bacteria  essential oil  lemon zest  sensory analysis  ?????? ???????  ??????? ??????????  ?????? ????????  ???? ???????  ???????? ?????? Index. décimale : 640 Industrie Alimentaire Résumé : This study was conducted in order to enhance the lemon peel (Citrus limon) by using their essential oil as a natural agent for preservation and aromatization in cream in order to diversify the types of existing cream on the market. This essential oil was extracted by hydroditillation, extraction yield was 0,89 ± 0,09%. The antioxidant activity of the extracted essential oil was studied by the DPPH° test, this free radical has been effectively reduced, compared to vitamin E. These results were confirmed by the test of β- carotene bleaching. The study of antimicrobial activity of essential oil of C. limon showed that two tested bacteria are resistant against the effectiveness of the oil, resulting in very high MICs (4% and > 8%). Regarding yeast strains isolated and tested Debaryomyces sp. and Rhodotorula sp., they have some sensitivity to the effect of essential oil, characterized by CMI respectively 0,25% and 0,5%. The other two strains Zygosaccharomyces sp1 and Zygosaccharomyces sp2, were resistant, their MICs are respectively in the order of 1% and > 4%. The various tests on the formulation of the added essential oil of C. limon creams were tested by developing three fresh creams with concentrations of 0,125%, 0,25%, 0,5%. Characteristics are conforms to standard. The results of physicochemical and microbiological analyzes prepared fresh cream after opening the package, show that the presence of the essential oil at low concentrations does not limit microbial spoilage. The evaluation of the oxidative stability by Schaal test indicates that the fresh cream with essential oil of C. limon are more resistant than the control opposite the forced oxidation. Sensory analysis show that the incorporation of essential oil in the cream, at concentrations of 0,125% and 0,25%, involves no significant difference (p > 0,05) in terms of flavoring, and make products which are classified in same order than the control. Only the rate of incorporation of the essential oil of 0,5% significantly downgraded the product compared to the control in the third row, which has led to changes in smell and flavor while the texture, color and taste are unchanged. The principal component analysis (PCA) showed a negative correlation (r = - 0,998) between the levels of incorporation of the essential oil and the aroma of raw milk, and a positive correlation (r = 0,956) with the color yellow. Diplôme : Magistère En ligne : ../theses/agronomie/KEH6360.pdf Format de la ressource électronique : pdf Permalink : https://bu.umc.edu.dz/md/index.php?lvl=notice_display&id=6352

Exemplaires (1)

Code-barres	Cote	Support	Localisation	Section	Disponibilité
KEH/6360	KEH/6360	Thèse	Bibliothèque principale	Thèses	Disponible