1,721,024 research outputs found
Isolation and Characterization of Cryotolerant Yeasts from Fiano di Avellino Grapes Fermented at Low Temperatures
Full text linkA fermentation of Fiano di Avellino grape must was carried out at 9°C with the aim of selecting cryotolerant yeast strains and testing their fermentative performances and volatile production following molecular characterization. A total of 20 yeast cultures were isolated at different fermentation stages. Based on molecular identification and characterization, Metschnikowia (M.) pulcherrima, Hanseniaspora (H.) uvarum, Staremerella (St.) bacillaris, Saccharomyces (S.) cerevisiae, S. kudriavzevii, and S. paradoxus were found to be the yeast species dominating the fermentation. S. paradoxus has been rarely isolated in vineyards and never in the cellar environment. Moreover, in this study, S. kudriavzevii is detected for the first time in vine-wine environments. Both S. kudriavzevii and S. paradoxus co-occurred with S. cerevisiae when grapes were micro-fermented at low temperatures. The growth kinetics of the three species were greatly affected by the fermentation temperature. As a consequence, Fiano wines obtained with S. kudriavzevii and S. paradoxus significantly differed from those made by S. cerevisiae in terms of chemical and volatile composition
Designing and evaluation of specific PCR primers for rapid and reliable identification of Staphylococcus xylosus strains isolated from fermented sausages.
No full textRapid and reliable identification of Staphylococcus xylosus was achieved by species-specific PCR assays. Two sets of primers, targeting on xylulokinase (xyl B) and 60 kDa heat-shock protein (hsp60) genes of S. xylosus, respectively, were designed. Species-specificity of both sets of primers was evaluated by using 27 reference strains of the DSM collection, representing 23 different species of the Staphylococcus genus and 3 species of the Kocuria genus. Moreover, 90 wild strains isolated from different fermented dry sausages were included in the analysis. By using primers xylB-F and xylB-R the expected PCR fragment was obtained only when DNA from S. xylosus was used. By contrast, amplification performed by using primers xylHs-F and xylHs-R produced a single PCR fragment, of the expected length, when DNA from S. xylosus, S. haemolyticus, S. intermedius and S. kloosii were used as template. Nevertheless, Alu I digestion of the xylHs-F/xylHs-R PCR fragment allowed a clear differentiation of these 4 species.
The rapidity (about 4 h from DNA isolation to results) and reliability of the PCR procedures established suggests that the method may be profitably applied for specific detection and identification of S. xylosus strains
Evoluzione della popolazione blastomicetica durante la produzione di olive da tavola di differenti cultivar siciliane monitorata attraverso l’analisi dell’ITS rDNA.
No full textLa popolazione blastomicetica di olive verdi da tavola, prodotte a partire da 4 diverse cultivar siciliane (Brandofino, Castriciana, Nocellara del Belice, Passulunara) e da una spagnola (Manzanilla), è stata monitorata durante l’intero processo di fermentazione. La tecnologia produttiva poteva definirsi di tipo semi-industriale, giacché il ruolo della microflora lattica era parzialmente sostituito dall’aggiunta di acido lattico e la fermentazione naturale avveniva in salamoia all’8% di NaCl. La popolazione di lieviti all’avvio del processo fermentativo è risultata, indipendentemente dalla cultivar di appartenenza, nell’ordine di 2.0 log UFC g-1. Viceversa nel prodotto al consumo le conte hanno rivelato livelli di popolazione blastomicetica variabili tra 5.5 e 6.5 log UFC g-1, con un valore massimo per la cultivar “Brandofino”. La tecnica rDNA ITS Restriction Endonucleases Analysis (ITS-RFLP) è stata adoperata per raggruppare 81 culture di lievito isolate durante il processo di produzione. L’impiego di tre differenti endonucleasi di restrizione (Cfo I, Hae III e Hinf I) ha generato tre soli profili ITS-RFLP. Il sequenziamento della regione D1/D2 del gene 26S rRNA ha consentito di stabilire che la specie più largamente rappresentata era Pichia kluyveri (88% degli isolati), mentre isolati rapportabili alle specie Candida parapsilosis e Pichia guilliermondii sono stati rinvenuti nella sola cultivar Brandofino ed esclusivamente su campioni di olive prima dell’avvio fermentativo. Le comunità blastomicetiche sono state altresì monitorate per analisi ITS rDNA sia su DNA estratto direttamente da olive, ovvero per approccio culture-independent, sia su DNA estratto da bulk cellulari da DRBC agar.
I ceppi isolati sono stati valutati per caratteristiche di interesse tecnologico quali produzione di H2S, attività β-glucosidasica, degradazione di citrato e lattato e attività lipolitica, onde comprendere il potenziale contributo protecnologico delle popolazioni blastomicetiche in questo prodotto.
Lavoro effettuato con il contributo dell’Istituto Regionale dell’Olio e dell’Olivo (IROO), Regione Sicilia
A comparison of statistical methods for identification of Streptococcus thermophilus, Enterococcus faecalis and Enterococcus faecium from Randomly Amplified Polymorphic DNA patterns
No full textCharacterization of Staphylococcus aureus isolated from a slaughterhouse for pigeons by RAPD-PCR and REA-PFGE
No full textGenetic Improvement of wine yeasts for opposite adsorption activity of phenolics and ochratoxin A during red winemaking
No full textThe aim of this research was to acquire new strains of Saccharomyces cerevisiae exhibiting opposite characteristics of cell wall adsorption: very high adsorption activity toward the ochratoxin A, very low adsorption activity toward the pigmented phenolic compounds contained in musts from black grapes. For this purpose, starting from 313 strains of Saccharomyces cerevisiae, 12 strains were pre-selected and used to obtain 27 intraspecific hybrids. Eleven crosses out of 27 were validated as hybrids; the best five hybrids were used in guided winemaking at four Calabrian wineries. The employed experimental protocol has allowed to select yeast strains for their different adsorption activity, improving the strains by spore clone selection and construction of intraspecific hybrids. These results suggest an efficacious way to improve the characteristics of interest in wine yeasts
Preliminare caratterizzazione di ceppi di Saccharomyces Cerevisiae isolati da campioni di Moscato Di Saracena (Calabria).
No full textBiotyping of Saccharomyces cerevisiae strains isolated from “Moscato of Saracena”, a southern Italy passito-wine (Calabria Region).
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