Search results for "lactococcus lactis"
showing 10 items of 74 documents
Influence of the early bacterial biofilms developed on vats made with seven wood types on PDO Vastedda della valle del Belìce cheese characteristics
2019
Early vat bacterial biofilms developed spontaneously through contact with whey have been characterized on seven wood types (Castanea sativa Miller, Cedrus libani, A. Rich., Prunus avium L., Fraxinus ornus L., Juglans regia L., Pinus nigra J.F. Arnold and Populus nigra L.). The present study aimed to evaluate the influence of these biofilms on the microbiological, chemical, physical and sensory characteristics of PDO Vastedda della valle del Belìce (VdB) cheese, processed traditionally from raw ewe's milk using wooden tools. To this purpose, the experimental cheeses after 15 d of refrigerated storage were examined. Lactic acid bacteria (LAB) populations dominated the microbial community of a…
Ecology and technological capability of lactic acid bacteria isolated during Grillo grape vinification in the Marsala production area
2011
Grapes of the “Grillo” variety, used to produce Marsala wine, were harvested from five vineyards with different climatic and agronomic parameters, in order to obtain a first mapping of lactic acid bacteria (LAB) inhabiting the production area. Marsala base wine production was followed at a large-scale, and also two experimental vinifications, with different lysozyme and SO2 concentrations and in combination, were carried out at pilot-plant scale. LAB communities and conventional chemical parameters were periodically analysed. LAB were found on grapes at an average concentration of about 102 CFU g−1 which decreased during the transformation process. A total of 146 colonies were collected, bu…
Effect of reducing agents on the acidification capacity and the proton motive force of Lactococcus lactis ssp. cremoris resting cells.
2002
International audience; Reducing agents are potential inhibitors of the microbial growth. We have shown recently that dithiothreitol (DTT), NaBH(4) and H(2) can modify the proton motive force of resting cells of Escherichia coli by increasing the membrane protons permeability [Eur. J. Biochem. 262 (1999) 595]. In the present work, the effect of reducing agents on the resting cells of Lactococcus lactis ssp. cremoris, a species widely employed in dairy processes was investigated. DTT did not affect the acidification nor the DeltapH, in contrast to the effect previously reported on E. coli. The DeltaPsi was slightly increased (30 mV) at low pH (pH 4) in the presence of 31 mM DTT or 2.6 mM NaB…
Characterization of two Lactococcus lactis zinc membrane proteins, Llmg_0524 and Llmg_0526, and role of Llmg_0524 in cell wall integrity
2015
Background Due to its extraordinary chemical properties, the cysteine amino acid residue is often involved in protein folding, electron driving, sensing stress, and binding metals such as iron or zinc. Lactococcus lactis, a Gram-positive bacterium, houses around one hundred cysteine-rich proteins (with the CX2C motif) in the cytoplasm, but only a few in the membrane. Results In order to understand the role played by this motif we focused our work on two membrane proteins of unknown function: Llmg_0524 and Llmg_0526. Each of these proteins has two CX2C motifs separated by ten amino-acid residues (CX2CX10CX2C). Together with a short intervening gene (llmg_0525), the genes of these two protein…
Cloning of branched chain amino acid biosynthesis genes and assays of alpha-acetolactate synthase activities in Leuconostoc mesenteroides subsp. crem…
1999
Abstract A genomic library from Leuconostoc mesenteroides subsp. cremoris (Lmc) in Escherichia coli was screened for α-acetolactate synthase (ALS) activity using a phenotypic test detecting the production of acetolactate or related C 4 derivatives (diacetyl, acetoin or 2,3-butanediol) in the culture. Four recombinant E. coli clones, with plasmids containing overlapping DNA fragments and displaying anabolic ALS activity, were selected. This activity is encoded by an ilvB gene belonging to a putative operon which contains genes highly similar to the genes of the branched chain amino acid (BCAA) operon of Lactococcus lactis subsp. lactis. This putative BCAA operon is not functional as the ilvA…
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…
Preliminary characterization of wine lactobacilli able to degrade arginine
2002
Lactobacillus strains able to degrade arginine were isolated and characterized from a typical red wine. All the strains were gram-positive, catalase-negative and produced both D- and L-lactate from glucose. Strains L2, L3, L4, and L6 were able to produce CO2 from glucose; however, production of CO2 from glucose was not observed in strains L1 and L5, suggesting that they belong to the homofermentative wine lactic acid bacteria (LAB) group. All of the lactobacilli were tested for their ability to ferment 49 carbohydrates. The sugar fermentation profile of strain L1 was unique, suggesting that this strain belonged to Lactococcus lactis ssp. cremoris, a non-typical wine LAB. Furthermore, a prel…
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…
Genetic organization of the mle locus and identification of a mleR-like gene from Leuconostoc oenos
1996
Characterization of the mle locus harboring the malolactic enzyme gene mleA and malate permease gene mleP from Leuconostoc oenos was completed in this study by mRNA analysis. Northern (RNA) blot experiments revealed a 2.6-kb transcript, suggesting an operon structure harboring mleA and mleP genes. Primer extension analysis showed that the mle operon has a single transcription start site located 17 nucleotides upstream of the ATG translation start site for the mleA gene. We found sequences, TTGACT and TATGAT (which are separated by 18 bp), that are closely related to the gram-positive and Escherichia coli consensus promoter sequences. Upstream of the mleA gene, an 894-bp open reading frame t…
Transfer, composition and technological characterization of the lactic acid bacterial populations of the wooden vats used to produce traditional stre…
2015
The biofilms of 12 wooden vats used for the production of the traditional stretched cheeses Caciocavallo Palermitano and PDO Vastedda della valle del Belìce were investigated. Salmonella spp. and Listeria monocytogenes were never detected. Total coliforms were at low numbers with Escherichia coli found only in three vats. Coagulase-positive staphylococci (CPS) were below the enumeration limit, whereas lactic acid bacteria (LAB) dominated the surfaces of all vats. In general, the dominance was showed by coccus LAB. Enterococci were estimated at high numbers, but usually between 1 and 2 Log cycles lower than other LAB. LAB populations were investigated at species and strain level and for thei…