Search results for "Bacteriocin"
showing 10 items of 34 documents
Codominance of Lactobacillus plantarum and obligate heterofermentative lactic acid bacteria during sourdough fermentation
2015
Fifteen sourdoughs produced in western Sicily (southern Italy) were analysed by classical methods for their chemico-physical characteristics and the levels of lactic acid bacteria (LAB). pH and total titratable acidity (TTA) were mostly in the range commonly reported for similar products produced in Italy, but the fermentation quotient (FQ) of the majority of samples was above 4.0, due to the low concentration of acetic acid estimated by high performance liquid chromatography (HPLC). Specific counts of LAB showed levels higher than 10(8) CFU g(-1) for many samples. The colonies representing various morphologies were isolated and, after the differentiation based on phenotypic characteristics…
In situ activity of a bacteriocin-producing Lactococcus lactis strain. Influence on the interactions between lactic acid bacteria during sourdough fe…
2005
Aims: To biochemically characterize the bacteriocin produced by Lactococcus lactis ssp. lactis M30 and demonstrate its effect on lactic acid bacteria (LAB) during sourdough propagation. Methods and Results: A two-peptide bacteriocin produced by L. lactis ssp. lactis M30 was purified by ion exchange, hydrophobic interaction and reversed phase chromatography. Mass spectrometry of the two peptides and sequence analysis of the ltnA2 gene showed that the bacteriocin was almost identical to lacticin 3147. During a 20-day period of sourdough propagation the stability of L. lactis M30 was demonstrated, with concomitant inhibition of the indicator strain Lactobacillus plantarum 20, as well as the …
Caseicin, a bacteriocin from Lactobacillus casei.
1993
The intracellular bacteriocin caseicin 80 was purified from cell extracts of Lactobacillus casei strain B80. It is a thermolabile protein with an apparent molar mass of 42 kDa. As no plasmids were observed in the bacteriocinogenic strain it is assumed that caseicin is encoded by the bacterial chromosome. Using 14C-labelled precursors it was found that biosynthesis of DNA and proteins was influenced by caseicin but this inhibition is probably not the primary effect. The incorporation of fructose but not of glucose into cellular material was inhibited by caseicin.
Vibrio cholerae cytolysin: assembly and membrane insertion of the oligomeric pore are tightly linked and are not detectably restricted by membrane fl…
2000
AbstractHemolytic strains of Vibrio cholerae secrete a cytolysin that, upon binding as a monomer, forms pentameric pores in animal cell membranes. Pore formation is inhibited at low temperature and in the absence of cholesterol. We here posed the following questions: firstly, can oligomerization be observed in the absence of pore formation? Secondly, is membrane fluidity responsible for the effect of temperature or of cholesterol upon pore formation? The first issue was approached by chemical cross-linking, by electrophoretic heteromer analysis, and by electron microscopy. None of these methods yielded any evidence of a non-lytic pre-pore oligomer. The second question was addressed by the u…
Production, stability, gene sequencing and in situ anti-Listeria activity of mundticin KS expressed by three Enterococcus mundtii strains
2014
Three enterococci (WFE3, WFE20 and WFE31) selected as presumptive bacteriocin producers were found to be active against Listeria monocytogenes. In this study, due to their potential industrial/food applications, the three bacterial isolates were extensively characterized. Identification was performed by means of a combined 16S rRNA gene sequencing and multiplex PCR approach, and was confirmed with the sequencing of a partial region of a protein-encoding gene, namely pheS. The three isolates belonged unequivocally to the species Enterococcus mundtii. The randomly amplified polymorphic DNA (RAPD) analysis recognized three distinct strains. The supernatants were mainly active against Listeria …
Biological control of Listeria monocytogenes in soil model systems by Enterococcus mundtii strains expressing mundticin KS production
2022
Abstract The agricultural practices applied in pre-harvest greatly influence the presence and the levels of microorganisms in fresh produce. Among these, Listeria monocytogenes represents one of the most lethal foodborne pathogens associated with vegetables. The main hypothesis of this work is that bacteriocin producer Enterococcus mundtii strains can be effective against L. monocytogenes in soil. To this purpose, bacteriocin production by E. mundtii WFE3, WFE20 and WFE31, three strains showing a strong bacteriocin activity in terms of inhibitory power and inhibition spectra, was evaluated in sterile extracts from agricultural soil and peat moss, in organic nutrient solution (ONS) and miner…
Microbial interactions in food model systems: In situ antilisterial activity of mundticin KS producing strains
2013
It is known that microbial interactions are important for the success of food fermentations, as well as for the establishment of the safety of the final products. In this study, we characterized extensively three enterococci (WFE3, WFE20 and WFE31) of flour origin, which were found to be active against Listeria monocytogenes, in order to investigate on their ability to produce bacteriocins in complex food model systems for their future industrial/food applications. The identification of the three bacterial isolates was performed by means of a combined 16S rRNA gene sequencing and multiplex PCR approach. Two isolates belonged unequivocally to the species E. mundtii, while one isolate could n…
Lactobacillus rossii sp. nov. isolated from wheat sourdough
2005
Screening of sourdough lactic acid bacteria for bacteriocin production resulted in the isolation of a Gram-positive, catalase-negative, non-spore-forming, non-motile rod bacterium (strain CS1T) that could not be associated with any previously described species. Comparative 16S rRNA gene sequence analysis recognized strain CS1T as a distinct member of the genus Lactobacillus. By a species-specific PCR strategy, five additional strains previously isolated from sourdoughs were found to belong to the same species as strain CS1T, as confirmed by 16S rRNA gene sequence analysis. The closest related species were Lactobacillus durianis, Lactobacillus malefermentans and Lactobacillus suebicus, with …
Caseicin 80: purification and characterization of a new bacteriocin from Lactobacillus casei
1990
When grown in complex or synthetic media, Lactobacillus casei B 80 synthesizes a mitomycin C-inducible polypeptide with very specific bactericidal activity against the sensitive strain Lactobacillus casei B 109. The amount of secreted bacteriocin in the culture solution was low, about 1 mg/l. The bacteriocin which we called caseicin 80, was also detectable in cell extracts, although only 2% of the total activity was retained intracellularly. Caseicin 80 was concentrated by ultrafiltration and purified by cation exchange chromatography with Cellulose SE-23 and Superose. The molecular weight was in the range of M r=40,000–42,000 and the isoelectric point was pH 4.5.
Extension of Tosela cheese shelf-life using non-starter lactic acid bacteria
2011
Six strains of non-starter lactic acid bacteria (NSLAB) were used to extend the shelf-life of the fresh cheese Tosèla manufactured with pasteurised cows’ milk. The acidification kinetics of three Lactobacillus paracasei, one Lactobacillus rhamnosus and two Streptococcus macedonicus were studied in synthetic milk medium. Lb. paracasei NdP78 and NdP88 and S. macedonicus NdP1 and PB14-1 showed an interesting acidifying capacity and were further characterised for growth in UHT milk and production of antimicrobial compounds. Lb. paracasei NdP78 and S. macedonicus NdP1 grew more than 2 log cycles in 6 h. Lb. paracasei NdP78 was also found to produce a bacteriocin-like inhibitory substance (BLIS) …