Search results for "ACID BACTERIA"
showing 10 items of 165 documents
Evolution of lactic acid bacterial populations during lysine fortification of sourdough breads by addition of pistachio powder
2019
Food fortification is a current practise to increase the bioavailability of certain nutrients. In this study, 5% (w/w) pistachio powder was added to tender wheat flour or durum wheat semolina to evaluate its contribution to augment the amount of lysine in bread. Bread production was carried out by sourdough technology using a selected 3-species lactic acid bacterial (LAB) starter culture (Lactobacillus sanfranciscensis PON100336, Leuconostoc citreum PON10079 and Weissella cibaria PON10030). In order to determine the influence of pistachio powder on the evolution of LAB, sourdough bread productions were compared with control trials obtained from flour or semolina and evaluated for the develo…
Effect of the mechanical harvest of drupes on the quality characteristics of green fermented table olives
2015
Background: Because of damage caused by mechanical harvesting, the drupes for table olive production are traditionally hand harvested. Until now, no data have been available on the microbiological and chemical features of mechanically harvested drupes during fermentation. Results: Drupes mechanically harvested and inoculated with Lactobacillus pentosus OM13 were characterized by the lowest concentrations of potential spoilage microorganisms. On the other hand, drupes mechanically harvested and subjected to spontaneous fermentation showed the highest concentration of Enterobacteriaceae and pseudomonads during transformation. The lowest decrease of pH (4.20) was registered for the trials inoc…
Ochratoxin A removal in synthetic media by living and heat-inactivated cells of Oenococcus oeni isolated from wines
2010
The capacity of Oenococcus oeni to eliminate ochratoxin A (OTA) from synthetic media in different conditions was studied. Ten tested O. oeni strains removed OTA from the medium but with significant differences depending on the strain, incubation period, and initial OTA level in the medium. Mycotoxin reductions higher than 60% were recorded in 14-day cultures spiked with 2 mu g OTA/l. Toxin removal was independent of bacterial viability and culture medium composition. This is the first study carried out to study OTA removal dynamics by living and heat-inactivated cells of O. oeni. The results aim that this bacterium may be a very useful tool to control OTA in food and beverages. (C) 2009 Els…
Mutation of the oxaloacetate decarboxylase gene of Lactococcus lactis subsp. lactis impairs the growth during citrate metabolism
2007
; Aims: Citrate metabolism generates metabolic energy through the generation of a membrane potential and a pH gradient. The purpose of this work was to study the influence of oxaloacetate decarboxylase in citrate metabolism and intracellular pH maintenance in relation to acidic conditions. Methods and Results: A Lactococcus lactis oxaloacetate decarboxylase mutant [ILCitM (pFL3)] was constructed by double homologous recombination. During culture with citrate, and whatever the initial pH, the growth rate of the mutant was lower. In addition, the production of diacetyl and acetoin was altered in the mutant strain. However, our results indicated no relationship with a change in the maintenanc…
Development of methods for the detection and quantification of spoilage microorganisms in wine : study of growing factors
2016
New practices used to elaborate wine lead to an increase of wine spoilage due to microorganisms. That is why, new technics have to be developed to quantify these microorganisms accurately, quickly and with low costs. The main wine spoilages are due to acetic acid bacteria (AAB) (A. aceti, A. pasteurianus, G. oxydans and Ga. liquefaciens) and Brettanomyces bruxellensis development. AAB transforms ethanol to acetic acid while B. bruxellensis transforms hydroxycinnamic acids to ethyl phenols (EP) (unpleasant odor molecules). In order to detect these wine spoilage microrganisms, flow cytometry coupled to fluorescent in situ hybridization has been assessed. No reproducible results have been deve…
Characterisation of films and nanopaper obtained from cellulose synthesised by acetic acid bacteria
2016
Bacterial cellulose (BC) samples were obtained using two culture media (glucose and glucose+fructose) and two bacteria (Komagataeibacter rhaeticus and Komagataeibacter hansenii). Nanopaper was obtained from the BC through oxidation and both were studied to determine the impact of culture media and bacteria strain on nanofiber structure and mechanical properties. AFM and SEM were used to investigate fibre dimensions and network morphology; FTIR and XRD to determine cellulose purity and crystallinity; carboxyl content, degree of polymerisation and zeta potential were used to characterise nanofibers. Tensile testing showed that nanopaper has up to 24 times higher Young's modulus (7.39GPa) than…
Il cibo come farmaco: probiotici, prebiotici, simbiotici
2004
Enteric microflora represent a protective barrier against infectious viruses, bacteria and toxins. Nutritional supplements constituted of live germs, producing and maintaining a condition of enteric eubioses may offer therapeutic possibilities against different pathologies.
Effects of yeast proteolytic activity on Oenococcus oeni and malolactic fermentation
2006
International audience; Alcoholic fermentation of synthetic must was performed using either Saccharomyces cerevisiae or a mutant Delta pep4, which is deleted for the proteinase A gene. Fermentation with the mutant Delta pep4 resulted in 61% lower levels of free amino acids, and in 62% lower peptide concentrations at the end of alcoholic fermentation than in the control. Qualitative differences in amino acid composition were observed. Changes observed in amino acids in peptides were mainly quantitative. After alcoholic fermentation each medium was inoculated with Oenococcus oeni. Malolactic fermentation in the medium with the Delta pep4 strain took 10 days longer than the control. This diffe…
Recovery Estimation of Dried Foodborne Pathogens Is Directly Related to Rehydration Kinetics.
2016
International audience; Drying is a common process which is used to preserve food products and technological microorganisms, but which is deleterious for the cells. The aim of this study is to differentiate the effects of drying alone from the effects of the successive and necessary rehydration. Rehydration of dried bacteria is a critical step already studied in starter culture but not for different kinetics and not for pathogens. In the present study, the influence of rehydration kinetics was investigated for three foodborne pathogens involved in neonatal diseases caused by the consumption of rehydrated milk powder: Salmonella enterica subsp. enterica serovar Typhimurium, Salmonella enteri…
Microbial characterisation of fermented meat productions from the Sicilian breed "Suino Nero dei Nebrodi"
2012
Two traditional sausage products (“salsiccia” and “salame”) processed from the raw meat of the Black Sicilian swine “Suino Nero dei Nebrodi” were microbiologically investigated during the manufacturing and ripening stages. Both products were dominated by lactic acid bacteria (LAB), especially rod-shaped types. The concentration of enterococci was consistent in salame. Coagulase-negative cocci increased slower than LAB. Yeasts showed an increasing trend during the ripening of both products. Enterobacteriaceae were counted at a constant level of about 105 CFU/g in both products, while pseudomonads diminished during ripening. Coagulase-positive staphylococci, Listeria monocytogenes and Salmone…