Search results for "Lactococcus lacti"
showing 5 items of 75 documents
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…
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…