Search results for "Lactococcus"
showing 10 items of 91 documents
Diversity and technological potential of lactic acid bacteria of wheat flours
2013
Abstract Lactic acid bacteria (LAB) were analysed from wheat flours used in traditional bread making throughout Sicily (southern Italy). Plate counts, carried out in three different media commonly used to detect food and sourdough LAB, revealed a maximal LAB concentration of approximately 4.75 Log CFU g−1. Colonies representing various morphological appearances were isolated and differentiated based on phenotypic characteristics and genetic analysis by randomly amplified polymorphic DNA (RAPD)-PCR. Fifty unique strains were identified. Analysis by 16S rRNA gene sequencing grouped the strains into 11 LAB species, which belonged to six genera: Enterococcus, Lactobacillus, Lactococcus, Leucono…
In-Depth Investigation of the Safety of Wooden Shelves Used for Traditional Cheese Ripening
2021
ABSTRACT The main goal of this research was to characterize the bacterial diversity of the wooden boards used for aging traditional Sicilian cheeses and to evaluate whether pathogenic bacteria are associated with these surfaces. Eighteen cheese dairy factories producing three traditional cheese typologies (PDO Pecorino Siciliano, PDO Piacentinu Ennese, and Caciocavallo Palermitano) were selected within the region of Sicily. The wooden shelf surfaces were sampled by a destructive method to detach wood splinters as well as by a nondestructive brushing to collect microbial cells. Scanning electron microscopy showed the presence of almost continuous bacterial formations on the majority of the s…
Genome sequence of Lactococcus garvieae UNIUD074, isolated in Italy from a lactococcosis outbreak.
2011
Lactococcus garvieae is the etiological agent of lactococcosis disease, affecting many cultured fish species worldwide. In addition, this bacterium is currently considered a potential zoonotic microorganism since it is known to cause several opportunistic human infections. Here we present the draft genome sequence of the L. garvieae strain UNIUD074.
Modification de la composition lipidique membranaire chez les bactéries lactiques en conditions de stress : étude du rôle physiologique des Acides Gr…
2010
The results obtained in this work have shown that in both lactic acid bacteria models, L. lactis subsp. cremoris and O. oeni, transcription of the cfa gene, encoding the Cfa synthase is stimulated when cells enter stationary phase of growth or when the cells are grown under stress conditions (acidic or presence of ethanol in the medium). The role of the CFAs has been apprehended by the comparative physiological analysis of the parental strain L. lactis subsp. cremoris and a Δcfa mutant generated in this strain. The high percentages of survival obtained in strains grown at pH 5.0 and undergoing acid stress (pH 3.0) prove that the cyclopropanation of unsaturated fatty acids is not essential t…
Inactivation of lactococcal aromatic aminotransferase prevents the formation of flora aroma compounds from aromatic amino acids in semi-hard cheese
1999
The enzymatic conversion of aromatic amino acids to aroma compounds plays a role in the formation of an undesirable floral aroma in Cheddar-like cheeses. In lactococci, the first step of aromatic amino acid degradation is a transamination, catalysed by an aromatic aminotransferase (AraT). We observed previously that in vitro, araT inactivation prevented degradation of aromatic amino acids and decreased degradation of Met and Leu. In this study we evaluated the effect of araT inactivation in Lactococcus lactis on flavour development in St. Paulin-type cheese. The degradation of amino acids was monitored by using radiolabelled amino acids and the volatile compounds formed were analysed by GC-…
Discovering lactic acid bacteria by genomics
2002
International audience; This review summarizes a collection of lactic acid bacteria that are now undergoing genomic sequencing and analysis. Summaries are presented on twenty different species, with each overview discussing the organisms fundamental and practical significance, environmental habitat, and its role in fermentation, bioprocessing, or probiotics. For those projects where genome sequence data were available by March 2002, summaries include a listing of key statistics and interesting genomic features. These efforts will revolutionize our molecular view of Gram-positive bacteria, as up to 15 genomes from the low GC content lactic acid bacteria are expected to be available in the pu…
Engineering a Saccharomyces cerevisiae Wine Yeast That Exhibits Reduced Ethanol Production during Fermentation under Controlled Microoxygenation Cond…
2006
ABSTRACTWe recently showed that expressing an H2O-NADH oxidase inSaccharomyces cerevisiaedrastically reduces the intracellular NADH concentration and substantially alters the distribution of metabolic fluxes in the cell. Although the engineered strain produces a reduced amount of ethanol, a high level of acetaldehyde accumulates early in the process (1 g/liter), impairing growth and fermentation performance. To overcome these undesirable effects, we carried out a comprehensive analysis of the impact of oxygen on the metabolic network of the same NADH oxidase-expressing strain. While reducing the oxygen transfer rate led to a gradual recovery of the growth and fermentation performance, its i…
Cyclopropane Fatty Acid Synthase from Oenococcus oeni: Expression in Lactococcus lactis subsp. Cremoris and Biochemical Characterization
2015
Bacterial cyclopropane fatty acid synthases (CFA synthases) catalyze the transfer of a methyl group from S-adenosyl-L-methionine (AdoMet) to the double bond of a lipid chain, thereby forming a cyclopropane ring. CFAs contribute to resistance to acidity, dryness, and osmotic imbalance in many bacteria. This work describes the first biochemical characterization of a lactic acid bacterium CFA synthase. We have overexpressed Oenococcus oeni CFA synthase in E. coli in order to purify the enzyme. The optimum cyclopropanation activity was obtained at pH 5.6 and 35.8 °C. The high K(m) (AdoMet) value obtained (2.26 mM) demonstrates the low affinity of O. oeni enzyme toward the L. lactis subsp. cremo…
Comparative analysis of production and purification of homo- and hetero-polysaccharides produced by lactic acid bacteria
2013
2 figuras, 2 tablas
Citrate permease gene expression inLactococcus lactissubsp.lactisstrains IL1403 and MG1363
1996
Citrate permease gene expression in the plasmid-free Lactococcus lactis strains IL1403 and MG1363 was studied. The ability to transport citrate results in diacetyl and acetoin production in IL1403 but not in MG1363. Citrate lyase, α-acetolactate decarboxylase, diacetyl and acetoin reductase were detected in IL1403. These data show that L. lactis ssp. lactis strain IL1403 is a citrate permease mutant of the biovar. diacetylactis. Immunological analysis revealed the α-and β-subunits of citrate lyase not only in IL1403 but also in MG1363 where no citrate lyase activity was found.