1,721,249 research outputs found
Valutazione del rischio nell’immissione deliberata di microrganismi geneticamente modificati (MGM) nell’ambiente
No full textNucleotide sequence and analysis of plasmid pMD136 from pediococcus pentosaceus FBB61 (ATCC43200) involved in pediocin. A production
No full textThe complete sequence of the 19515-bp plasmid pMD136 from Pediococcus pentosaceus FBB61 (ATCC43200) has been determined. This plasmid is involved in Pediocin A production, a bacteriocin active against a wide range of gram- positive bacteria. It appears to replicate via a theta mechanism, with structures closely related to those of many lactococcal plasmids. Genes homologous to mobilization functions are also present, which are similar in sequence and arrangement to mobA, mobB, and mobC of some staphylococcal plasmids, although the last one contains a deletion in its central part. The region involved in bacteriocin activity has been limited to a 9.4-kb fragment, containing 10 open reading frames organized in a single operon. Since Pediocin A has a molecular weight of about 80 kDa (Piva and Headon, Microbiology, 140, 697-702, 1994), and a gene long enough to encode it is not present in pMD136, it is proposed that genes residing on the plasmid are responsible for the regulation of bacteriocinogenic activity. Gene arrangement and sequence homologies suggest the presence of a two-component- like regulatory mechanism. (C) 2000 Academic Press
Optimization of fluorescence microscopy techniques for the detection of total and viable lactic acid bacteria in whey starter cultures
No full textThis work aimed at studying the applicability of the most widely used fluorescence microscopy techniques to evaluate total and viable bacteria in a complex matrix
such as natural whey from Grana Padano cheese production. Fluorescein diacetate, BacLight, CTC (5-cyano-2,3-ditolyl tetrazolium chloride), DAPI (4’,6-diamidino-2-
phenylindole), and acridine orange stainings were evaluated on pure cultures and optimised for their use directly on natural whey starter cultures. Different incubation times and
resuspension buffers were tested. The developed procedures allow the enumeration of both viable and dead bacterial cells directly on the whey matrix. The methods proposed
may be used to directly evaluate the metabolic state of bacterial populations present in whey starter cultures
Attività β-glucosidasica di lieviti isolati da vinacce per la produzione di Grappa
No full textMicrobial glycosidase activity contributes to the aroma of wines and distillates through the hydrolysis of flavourless glycosilated compounds, present in grape skins, that release free terpenols and other aromatic compounds. Grappa, a typical Italian alcoholic product, is obtained from the distillation of grape marcs, that are mainly composed of grape skins, after a variable period of storage. The present work was aimed at analysing the β-glucosidase activity of yeasts isolated during the insilage period from grape marcs with different characteristics, such as origin (Moscato or Prosecco grapes), or technological treatments carried
out during this period. β-glucosidase activity was detected using a fluorimetric method based on the emission of a fluorescent signal from a molecule containing a glycoside
bond. Assays were conducted reproducing typical conditions of the oenological environment, and this method allowed us to rapidly and precisely quantify the enzymatic activity, so that a large number of yeasts could be examined.
L’attività glucosidasica dei microrganismi contribuisce all’aroma dei vini e dei distillati attraverso l’idrolisi dei composti glicoconiugati inodori, concentrati negli acini, che rilasciano terpenoli liberi ed altri composti aromatici. La Grappa, tipica bevanda alcolica italiana, si ottiene dalla distillazione della vinaccia, composta principalmente dalle bucce d’uva, dopo un periodo di stoccaggio variabile. Questo lavoro ha avuto lo scopo di analizzare l’attività β-glucosidasica di ceppi di lievito isolati da vinacce di diversa origine (Moscato e Prosecco) o sottoposte a trattamenti tecnologici. L’attività β-glucosidasica è stata saggiata utilizzando un metodo, appositamente messo a punto, basato sull’emissione di un segnale fluorescente da parte di una
molecola contenente un legame glicosidico. I saggi sono stati condotti riproducendo le condizioni tipiche dell’ambiente enologico e hanno permesso di quantificare rapidamente l’attività enzimatica di un numero elevato di lieviti
Valutazione dell'attivita beta-glucosidasica di lieviti isolati da vinaccia destinata alla produzione di grappa
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