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At least 613 records · Page 34Linked to original sources

Survival of lactic acid bacteria in seawater: a factorial study.

A feasibility study of lactic bacteria as potential probiotics in larval cultures of marine fish was performed by investigating the survival of five strains of lactic bacteria in seawater by readily standardized procedures at different temperatures and salinities. These conditions were chosen in such a way that their combinations define a complete first-order factorial design. Depending on the strain and the ambient conditions, the survival adhered to first-order kinetics in some cases, and to the Gompertz equation in others. The half lives (t0.5) calculated from these models were subsequently introduced as responses to the factorial designs, estimating the coefficients of empirical equations that describe the group effect of temperature and salinity on t0.5. Simply additive effects were found in two cases, a negative first-order interaction in another case, while another two required second-order models.

Colony Count, Microbial↗

Microbiological analysis of 5-formyltetrahydrofolic acid and other folates using an automatic 96-well plate reader.

The growth of auxotrophic bacteria remains the method of choice for the determination of biologically active folate metabolites in plasma. This report describes a microbiological assay for folates adapted to use disposable 96-well plates and an automatic plate reader. The modifications in the assay decreased reagent costs and made the analysis of hundreds of samples per day possible with a sensitivity limit of 10 fmol of (6S)-5-formyltetrahydrofolic acid. This limit compares favorably with that of previously reported, more laborious methods. The unnatural 6R diastereomer of 5-formyltetrahydrofolic acid did not interfere with the microbiological assay of the natural 6S diastereomer.

Autoanalysis↗

Comparative evaluation of two methods of enumerating enterococci in foods: collaborative study.

Two methods of enumerating enterococci in foods were compared in a collaborative study. Thirteen laboratories tested four blind duplicate samples containing different levels of enterococci and two negative control samples. Freeze-dried mixtures of bacteria were used as simulated food samples. The freeze-dried samples were reconstituted and either spread directly on the surface of Slanetz and Bartley medium (SB) and incubated at 44 degrees C for 48 h or preincubated in tryptone soya agar at 37 degrees C for 2 h before being overlaid by SB and incubated at 37 degrees C for a further 46 h. The numbers CFU of enterococci recovered by the two methods were not significantly different except for one sample where the 37 degrees C method gave a somewhat higher recovery. The 44 degrees C method was less time-consuming and less laborious.

Animals↗

Characterization of bacteriocins from Enterococcus faecium with activity against Listeria monocytogenes.

Laboratory cultures and environmental isolates of bacteria were screened for antagonism towards Listeria monocytogenes using an agar spot test. Seven of the 163 strains that were tested, one Streptococcus bovis, one Enterococcus casseliflavus, two E. avium and three E. faecium, consistently displayed antilisterial activity. Cell-free, pH-neutralized supernatants prepared from the three E. faecium strains (JBL1061, JBL1083 and JBL1351) exhibited strong antilisterial activity against L. monocytogenes, and were subjected to more detailed analyses. The antagonistic factors produced by these three strains were sensitive to chloroform and several proteolytic enzymes, resistant to heat (121 degrees C, 20 min), and stable over a wide pH range (3.0-10.0). Moreover, they were listericidal without causing cell lysis. These data suggest that a bacteriocin(s) is involved in the inhibition of L. monocytogenes by E. faecium JBL1061, JBL1083 and JBL1351.

Bacteriocins↗

Microbiological and aromatic characteristics of fermented maize doughs for kenkey production in Ghana.

A very uniform microflora was demonstrated in 15 samples of fermented maize dough from different larger commercial production sites. At the advanced stage of fermentation, more than 96% of the bacteria present were morphologically and biochemically uniform, obligatively heterofermentative lactobacilli occurring in concentrations about 10(9) cfu/g. Yeast occurred in levels of about 10(6) cfu/g, dominated by Candida and Saccharomyces spp. Studies on microbial successions indicated a selection towards a micropopulation dominated by lactic acid bacteria. The Gram-negative bacteria, catalase-positive Gram-positive bacteria and moulds underwent three to four decimal reductions during the early phase of the process. The aroma components detected were dominated by lactic acid, acetic, butyric and propionic acids. Volatile aroma components demonstrated by gas chromatography and mass spectrometry were characteristic for lactic acid bacteria with acetoin and related products as typical examples.

Bacteria↗

Comparison of electrophoretic distribution patterns of ribosomal RNA gene restriction fragments and of ribosomal subunit proteins of Lactococci, Streptococci, and Pediococci.

Comparison of electrophoretic distribution patterns of ribosomal RNA gene restriction fragments and of ribosomal subunit proteins are equally effective procedures for detecting differences and similarities in the Lactococci, Streptococci and Pediococci examined. Electrophoretic distribution patterns of ribosomal subunit proteins may be a useful tool in taxonomic studies.

DNA, Ribosomal↗

Development of a disposable pyruvate biosensor to determine pungency in onions (Allium cepa L.).

A disposable prototype pyruvate biosensor was constructed using pyruvate oxidase immobilised on mediated meldolas blue electrodes to determine pungency in onions (Allium cepa L.). The optimum operating potential was +150 mV (versus Ag/AgCl). A strong correlation between the biosensor response and untreated onion juice of known pyruvate concentration 2-12 micromol/g fresh weight (FW) was demonstrated. The biosensor was able to differentiate between low and high pungency onions. The detection limit using 1 unit of pyruvate oxidase was 1-2 micromol/g FW. Optimum concentrations of co-factors TPP, FAD and MgSO4 comprising the enzyme cocktail were determined as being 0.04, 0.1 and 30 mM, respectively.

Biosensing Techniques↗