Search results for "lactis"
showing 10 items of 92 documents
Transport of Sugars and Sugar Alcohols by Lactic Acid Bacteria
2008
Lactic acid bacteria (LAB) play an important role in the fermentation of beverages like wine and beer, and in the production of dairy products, sour dough, sausages and cheese. The knowledge of the genome sequence offers an insight into the metabolism of the bacteria and provides means to optimize the manufacturing of the products. By now genomes of several lactic acid bacteria are sequenced, including wine related bacteria Oenococcus oeni PSU-1, Pediococcus pentosaceus ATCC 25745, Leuconostoc mesenteroides ATCC 8293 (http://www.jgi.doe.gov/; Klaenhammer et al. 2002; Mills et al. 2005) and Lactobacillus plantarum WCFS1 (http://www.cmbi. ru.nl/plantarum/; http://www.lacplantcyc.nl/; Kleerebe…
Retention of aroma compounds by lactic acid bacteria in model food media
2008
The interactions between aroma compounds and other particles in foods, particularly with macromolecules, have been greatly studied in order to better understand the binding of flavors in food matrices. Bacteria possess many macromolecules on their cellular surface that provide them surface properties which are involved in the physicochemical interactions between cells and interfaces. However, the interactions between bacteria and aroma compounds have not received so much attention despite the presence of bacteria in many fermented products. In order to study the retention of aroma compounds by bacteria, we have investigated the retention of esters by lactic acid bacteria with static headspa…
Kinetics of citrate uptake in growing cells ofLeuconostocspp.
1996
Citrate uptake was studied in growing cells of Leuconostoc mesenteroides subsp. mesenteroides. A Michaelis-Menten pattern with the dianionic form of citrate as the limiting substrate has been proposed. It was validated for different fermentations varying the initial citrate concentrations and the pH medium. This latter did not modify the rate of the process which was clearly confirmed using experiments with resting cells. The model was used to compare the kinetics of citrate consumption between several strains of Leuconostoc mesenteroides subsp. mesenteroides, Leuconostoc mesenteroides subsp. cremoris and Leuconostoc lactis.
Dominant Lactic Acid Bacteria in Naturally Fermented Milks from Messinese Goat’s Breed
2019
Background: Lactic Acid Bacteria (LAB) are an important group of microorganisms responsible for the fermentation dairy products. This study was done to identify the dominant lactic acid bacteria in naturally fermented milks from Messinese goat’s breed. Methods: Eighteen individual raw milk samples collected from Messinese goat’s breed were acidified at pH 5.20 and left to spontaneously ferment at 37 °C for 4 days. All samples were analyzed for rod- and coccus-shaped LAB. Also, all presumptive LAB were isolated and differentiated according to their phenotypic properties and genetic polymorphisms and then identified by sequencing the 16S rRNA gene. Data were statistically analyzed using SAS 9…
Contribution of exofacial thiol groups in the reducing activity of Lactococcus lactis
2010
Lactococcus lactis can decrease the redox potential at pH 7 (E(h7)) from 200 to -200 mV in oxygen free Man-Rogosa-Sharpe media. Neither the consumption of oxidizing compounds or the release of reducing compounds during lactic acid fermentation were involved in the decrease in E(h7) by the bacteria. Thiol groups located on the bacterial cell surface appear to be the main components that are able to establish a greater exchange current between the Pt electrode and the bacteria. After the final E(h7) (-200 mV) was reached, only thiol-reactive reagents could restore the initial E(h7) value. Inhibition of the proton motive force showed no effect on maintaining the final E(h7) value. These result…
Dairy Debaryomyces hansenii strains produce the antihypertensive casein-derived peptides LHLPLP and HLPLP
2015
The ability of dairy Debaryomyces hansenii, Kluyveromyces lactis and Kluyveromyces marxianus strains to release the casein-derived antihypertensive sequences RYLGY, AYFYPEL, LHLPLP, HLPLP, VPP and/or IPP was examined. Yeast strains were grown in medium with casein as sole nitrogen source and the yeast casein hydrolysates (CSHs) were analysed by HPLC-MS/MS to search for the six antihypertensive sequences. Only LHLPLP and HLPLP were identified in CSHs and exclusively in D. hansenii Dh1 and Dh14 hydrolysates in which both antihypertensive sequences represented approximately 6 (CSH Dh1) and 10% (CSH Dh14) of total peptide content. In addition, a complete analysis of selected CSHs by HPLC-MS/MS …
Proton-dependent kinetics of citrate uptake in growing cells ofLactococcus lactissubsp.lactisbv.diacetylactis
1995
The kinetic analysis of citrate uptake in growing cells of Lactococcus lactis subsp. lactis biovar. diacetylactis identified a proton-dependent transport and suggested the divalent anionic species as the form of citrate transported across cell membranes. The reaction followed Michaelis-Menten kinetics for a two-substrate reaction. The limiting steps were the formation of the ternary complex and the rate of transport. Temperature modified the activity of the permease, increasing the uptake rate.
The comparative behavior of Lactococcus lactis in free and immobilized culture processes
1998
This study presents the changes in the physiological state of Lactococcus lactis in different actively growing systems. The intracellular pH (pHin), NADH/NAD ratio and lactate dehydrogenase (LDH) activity were measured in free cell batch culture with or without external pH (pHout) control, and in continuous free or immobilized cell reactors. In free cell batch culture it has been shown that the pHin is dependent both on pHout and age of the culture, while in free cell continuous culture the pHin and the pHout are close together. The NADH/NAD ratio varied inversely with the growth rate, which was related to the changes in the metabolic activities in lactococci. The specificity of the immobil…
Design of biopolymeric matrices entrapping bioprotective lactic acid bacteria to control Listeria monocytogenes growth: Comparison of alginate and al…
2014
In order to design biopolymeric matrices entrapping bioprotective lactic acid bacteria (LAB) to control undesirable microorganisms growth in foods, the performances of alginate and alginate-caseinate (an aqueous two-phase system) matrices entrapping Lactococcus lactis subsp. lactis LAB3 cells were compared. Since efficient matrices should preserve the culturability and the antimicrobial activity of entrapped LAB3 cells for prolonged periods, they were both monitored for 12 days storage at 30 °C. Maximal cell density (∼109 CFU mL−1) was reached after 24 h whatever the matrix type. Then, the LAB3 cells population decreased: 107 and 106 CFU mL−1 were enumerated after 12 days in alginate-casein…
Different Modes of Regulation of the Expression of Dextransucrase in
2019
Leuconostoc lactis AV1 strain isolated from a Tunisian avocado was characterized as a dextran producer. The promoter PdsrLL and the dsrLL gene encoding the DsrLL dextransucrase responsible for the dextran synthesis were transcriptionally fused to the mCherry coding gene generating the pRCR20 plasmid. Upon plasmid transfer, both AV1n and the dextran non-producing Leuconostoc mesenteroides CM70 became red due to expression of the mCherry from the PdsrLL-dsr-mrfp transcriptional fusion. Characterization of the polymers present in cultures supernatants revealed that the DsrLL encoded from pRCR20 in the recombinant bacteria was able to synthesize dextran. The production of dextran by the DsrLL i…