117,650 research outputs found
Molecular techniques in the microbial ecology of fermented foods
No full textThanks to the application of methods allowing precise imaging of microbial ecology, the field of food fermentation has experienced exponential growth in the last few years. This has resulted in the availability of new information on the structure and dynamics of the microbial populations during fermented food production. Molecular Methods and Microbial Ecology of Fermented Foods presents the latest findings in microbial ecology as determined by the application of molecular methods, reports the most recent advances in the field, and offers details on primers and protocols most suitable for studying specific food ecosystems. It provides analytical details and suggestions useful in research, as well as evaluation of the criticism of using novel approaches in food fermentation microbiology. This book also discusses new insights drawn from the use of bio-molecular techniques in the microbial ecology of fermented foods
USE OF A CULTURE-INDEPENDENT MOLECULAR METHOD FOR THE DIRECT DETECTION ANIDENTIFICATION OF YERSINIA SPP. IN FOOD
No full textA culture-independent method for the direct detection in food of Yersinia spp. was developed in this study. It is based on the
amplification of a 359 bp PCR product from the RNA polymerase beta-subunit gene (rpoB) and subsequent analysis by
denaturing gradient gel electrophoresis (DGGE). Direct detection of Yersinia spp. by PCR–DGGE was carried out in ready-toeat
vegetables and the results compared with the results of the traditional, culture-dependent method. The DGGE profiles were
determined to be species-specific. As a matter of fact, Yersinia enterocolitica, Yersinia intermedia, Yersinia frederiskenii and
Yersinia kristensenii showed differential migrations in the gels. Moreover, Y. enterocolitica serotypes O:3, O:5 and O:9 were
distinguishable, as well. Only for a limited number of traditionally isolated strains, the biochemical and molecular identification
agree. In particular, an overestimation of Y. enterocolitica, as determined biochemically, was observed. Finally when the
protocol was applied to 27 food samples, a good correlation was obtained when the results of traditional and direct methods
were analyzed. The molecular method was able to identify Y. enterocolitica, not detected by plating analysis. However, for 4
samples, that, by plating analysis, were determined to contain Yersinia spp., no PCR product could be obtained after
enrichment, probably due to low numbers of target cells, thereby not allowing the possibility to perform DGGE analysis.
The protocol described here represents a reliable tool for the detection of Yersinia spp. in food, which can be used to obtain the
needed results faster than with traditional culturing methods
Molecular and technological characterization of Staphylococcus xylosus isolated from naturally fermented Italian sausages by RAPD, Rep-PCR and Sau-PCR analysis
No full textCoagulase-negative cocci (CNC) are important microorganisms in fermented sausages because they release lipases and proteases that are able to free short-chain fatty acids and peptides and aminoacids, respectively, that are responsible for the aroma of fermented sausage. The purpose of this study was to characterize Staphylococcus xylosus strains isolated from naturally fermented sausages, produced in three different processing plants in the Friuli Venezia Giulia region in the Northeast of Italy. Two hundred and forty-nine strains of S. xylosus were identified by species-specific PCR and subjected to molecular and technological characterization. RAPD-PCR with primer M13, Rep-PCR using primer (GTG)5 and Sau-PCR with primer SAG1 were used for the molecular analysis, while the capability of the strains to grow at different temperatures and in the presence of NaCl and their lipolytic and proteolytic activity were tested in order to define the technological characteristics. The results obtained allowed us to differentiate strains coming from different plants, thereby admitting the presence of strains that are plant-specific. © 2006 Elsevier Ltd. All rights reserved
Development of a rapid method for the identification of Lactobacillus spp. isolated from naturally fermented Italian sausages using a polymerase chain reaction-temperature gradient gel electrophoresis
No full textA rapid method for the identification of Lactobacillus spp. isolated from naturally fermented Italian sausages was developed. It is based on the amplification of a small fragment from the 16S rRNA gene followed by temperature gradient gel electrophoresis (TGGE). Luctobacillus sakei, L. curvatus, L. alimentarius, L. casei, L. plantarum and L. brevis, obtained from International Collections, were used to optimize the method. Thiry-nine strains of Lactobacillus spp. were isolated from naturally fermented sausages and, after traditional identification, were tested by the PCR-TGGE protocol developed. No differences were observed comparing the results obtained, apart from five strains identified as L. curvatus that showed a PCR-TGGE profile identical to L. sakei
Ricerca di patogeni in branzini, orate e cefali con metodiche biomolecolari (PCR). Valutazione di metodologie per prolungare la shelf-life
No full textThe aim of the work was to study the presence of Campylobacter jejuni and C. coli, Salmonella spp., L. monoeytogenes, E. coli O157:H7, and Yersinia enterocolitica in Mediterranean Sea Bass (Dicentrarchus labrax), Gilt-bream (Sparus aurata) and Grey Mullet (Mugil cephalus) collected from supermarkets of the North of Italy. Then the dynamic of microorganisms population in Mediterranean Sea Bass packaged in MAP or under vacuum and kept at 3°C or stored on ice was also studied. The results demonstrated the high quality of fishes sold in supermarkets and that MAP and under vacuum technology can increase the shelf-life of fish
Direct identification in food samples of Listeria spp. and Listeria monocytogenes by molecular methods
No full textA new molecular approach for the detection and identification of Listeria spp. and Listeria monocytogenes in food is presented here. The method is based on the PCR amplification of a fragment of the iap gene from the five species belonging to the genus and on the analysis of the PCR products obtained by denaturing gradient gel electrophoresis (DGGE). The protocol was first optimized by using strains from international collections. Based on the differences present in the sequences amplified, it was possible to obtain species-specific DGGE migration that allowed fast and easy identification of L. monocytogenes, L. innocua, L. welshimeri, L. seeligeri, and L. ivanovii. Moreover, for L. monocytogenes serotypes, partial differentiation was possible. The optimized protocol was used for identification of Listeria strains traditionally isolated from food and for direct detection and identification of Listeria members in food after an overnight enrichment. Identification of 48 food isolates and direct detection of Listeria spp. in 73 food samples show the potential of the method that can be used as a fast screening test to investigate the presence of Listeria spp. and L. monocytogenes in food
A PCR-Microplate Capture Hybridization Method to Detect Listeria monocytogenes in Blood
No full textn order to improve the diagnosis of Listeria monocytogenes infection, we have developed a polymerase chain reaction (PCR)-based assay combined with microplate capture hybridization technique. The system is based on selective amplification of L. monocytogenes with two specific primers based on the iap gene. The amplicon produced, with digoxigenin 11-dUTP incorporated during PCR, is hybridized in streptavidin-coated microtitre plates prepared with biotinylated specific DNA probe. The method involved requires approximately 6-8 h, and its high sensitivity, rapidity and simplicity should make it valuable for diagnosis and for epidemiological studies of listeriosis
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