Search results for "Lactococcus"
showing 10 items of 91 documents
Effect of different mineral salt mixtures and dough extraction procedure on the physical, chemical and microbiological composition of Şalgam: A black…
2021
NaCl is utilized in Salgam at 1-2% (w/w). The aim of this study was to reduce the NaCl content by addition of different concentrations of KCl and CaCl2 during production and evaluate their effects on quality. An innovation in production process was also employed, specifically dough extraction and use of the resulting liquid as a starter inoculum. Lactic acid bacteria (LAB) species (13) were identified using a combined approach of (RAPD)-PCR and 16S rRNA gene sequencing. Lactobacillus paracasei and Lactobacillus plantarum were dominant, but Leuconostoc mesenteroides subsp. jonggajibkimchii, Lactococcus lactis subsp. cremoris, Lactobacillus coryniformis subsp. coryniformis, Lactobacillus para…
Understanding of the physiological and genetic mechanisms involved in the reducing activity of Lactococcus lactis
2015
Lactic acid bacteria, particularly Lactococcus lactis are used in dairy industry. These bacteria are known to have a reducing activity, indicating their ability to lower the redox potential (Eh) of a medium. L. lactis MG1363 genome encodes several proteins with a CXXC motif, potentially linked with a redox activity. To understand the role of proteins rich in cysteine located at the surface of L. lactis, two approaches were used, one bioinformatics and biochemical another. For bioinformatic approach, interest was focused on two proteins of unknown function and CX2CX10CX2C motif: Llmg_0524 and Llmg_0526. Their corresponding genes form an operon temporarily induces in early growth phase. In th…
Use of Gases in Microorganism Preservation Processes
2019
International audience
Kinetics of lactate fermentation and citrate bioconversion by LactococcusIactisssp.Iactisin batch culture
1993
The growth kinetics of Lactococcus lactis ssp. lactis were studied in batch culture in conditions of non-limiting lactose and the presence of citric acid. The control of pH modified growth and citrate metabolism but did not change the yield of acid formation. At controlled pH the growth rate was unaffected by citrate metabolism. Lactose was transformed to L-lactate and assay of the metabolic by-products showed some heterofermentation at the end of the growth of cultures with low growth rates. This heterofermentation was interpreted as a slowing down of glycolysis with activation of both the pyruvate formate lyase (PFL) and the pyruvate dehydrogenase complex (PDHC). Under these conditions th…
Comparison of α-acetolactate synthase and α-acetolactate decarboxylase in Lactococcus spp. and Leuconostoc spp.
1994
Cell-free extracts of Leuconostoc and Lactococcus species were tested for their alpha-acetolactate synthase and alpha-acetolactate decarboxylase activities. In Leuconostoc mesenteroides subsp. cremoris, Leuconostoc mesenteroides subsp. mesenteroides and Leuconostoc lactis, the Km of alpha-acetolactate synthase for pyruvate was close to 10 mM whereas it was 30 mM in Lactococcus lactis subsp. lactis biovar. diacetylactis. The Km of alpha-acetolactate decarboxylase for alpha-acetolactic acid was very low (0.3 mM) in Leuconostoc species in comparison to Lactococcus lactis subsp. lactis biovar. diacetylactis (60 mM). In the latter bacterium, alpha-acetolactate decarboxylase showed a sigmoidal de…
Biodiversity and dairy traits of indigenous milk lactic acid bacteria grown in presence of the main grape polyphenols
2020
ABSTRACT The present work was developed to select lactic acid bacteria (LAB) to be used as starter cultures in functional cheese production. The indigenous milk LAB populations were isolated from fermented raw ewes’ milks (four bulks) added with 0.5 mg/mL of nine polyphenols commonly found in winery by-products. After 48 h of fermentation, all milks were characterized by an increase of LAB levels of about 3–4 Log cycles. All different colonies were purified and characterized for the main physiological and biochemical traits and then differentiated genetically at strain level and identified. Ten species belonging to the LAB genera Lactobacillus, Streptococcus, Enterococcus, Leuconostoc and L…
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…
Advanced Strategies for Food-Grade Protein Production: A New E. coli/Lactic Acid Bacteria Shuttle Vector for Improved Cloning and Food-Grade Expressi…
2019
Food-grade production of recombinant proteins in Gram-positive bacteria, especially in LAB (i.e., Lactococcus, Lactobacillus, and Streptococcus), is of great interest in the areas of recombinant enzyme production, industrial food fermentation, gene and metabolic engineering, as well as antigen delivery for oral vaccination. Food-grade expression relies on hosts generally considered as safe organisms and on clone selection not dependent on antibiotic markers, which limit the overall DNA manipulation workflow, as it can be carried out only in the expression host and not in E. coli. Moreover, many commercial expression vectors lack useful elements for protein purification. We constructed a &ld…