Behavior of Lactococcus lactis subsp. lactis biovar. diacetylactis in a Four Lactococcus Strain Starter during Successive Milk Cultures

2008 ◽  
Vol 14 (6) ◽  
pp. 469-477 ◽  
Author(s):  
M. Dalmasso ◽  
S. Prestoz ◽  
V. Rigobello ◽  
Y. Demarigny
Keyword(s):  
Lactococcus Lactis ◽  
Dairy Products ◽  
Selective Advantage ◽  
The Other ◽  
Controlled System ◽  
Lactococcus Lactis Subsp ◽  
Citrate Metabolism ◽  
Potential Factors ◽  
Sterilized Milk ◽  
Ppm Level

Cheeses are frequently made with natural whey starters (NWS). The whey from the previous cheese making is cultured and used for the next day. This practice, although essential for the development of typical sensory characteristics, can sometimes lead to acidification defects. In this work, the ability of Lactococcus lactis subsp. lactis biovar. diacetylactis to dominate over the other lactic acid bacteria (LAB) was tested in a controlled system as a possible explanation for these acidification breakdowns. A starter made of two Lc lactis subsp. lactis strains (LL), one Lc lactis subsp. cremoris strain (LC), and one Lc lactis subsp. lactis biovar. diacetylactis (LD) was added to sterilized milk. After incubation, the whey was removed and used to re-seed sterilized milk, the next day. This process was made during a five and twelve days' period. During the eight first days, the proportion of LD population increased, while the other LAB remained rather stable. Thereafter, LD strains dominated. At the same time, the diversity of LD population diminished considerably. If acidification ability of these LAB is not altered, this simplification was particularly hazardous in case of phages attack. LC and LL behavior was tested in milk containing increasing diacetyl concentrations. As long as diacetyl did not exceed a 5 ppm level — frequently measured in dairy products — its influence was impossible to detect. The selective advantage conferred by the citrate metabolism was proposed as a possible explanation for the LD population dominance. Other potential factors were also examined.

scholarly journals Complete Genome Sequence of Lactococcus lactis subsp. lactis bv. diacetylactis SD96

2020 ◽  
Vol 9 (3) ◽  
Author(s):  
Robin Dorau ◽  
Jun Chen ◽  
Peter Ruhdal Jensen ◽  
Christian Solem
Keyword(s):  
Lactococcus Lactis ◽  
Proteolytic Activity ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Complete Genome ◽  
Phage Resistance ◽  
Content Type ◽  
Lactococcus Lactis Subsp ◽  
Citrate Metabolism ◽  
Cheese Production

The genome of Lactococcus lactis subsp. lactis bv. diacetylactis SD96, a strain used for cheese production, is presented. SD96 is refractory to phage attack, which is a desired property for starter bacteria. Its 10 plasmids provide industrially important traits, such as lactose and citrate metabolism, proteolytic activity, and phage resistance.

Persistence of Escherichia coli O157:H7 in Dairy Fermentation Systems

1998 ◽  
Vol 61 (12) ◽  
pp. 1602-1608 ◽  
Author(s):  
SEAN S. DINEEN ◽  
KAZUE TAKEUCHI ◽  
JANE E. SOUDAH ◽  
KATHRYN J. BOOR
Keyword(s):  
Escherichia Coli ◽  
Lactococcus Lactis ◽  
Dairy Products ◽  
Starter Cultures ◽  
Escherichia Coli O157 ◽  
Potential Health ◽  
E Coli ◽  
Lactococcus Lactis Subsp ◽  
Fermented Dairy Products ◽  
Fermented Dairy

We examined (i) the persistence of Escherichia coli O157:H7 as a postpasteurization contaminant in fermented dairy products; (ii) the ability of E. coli O157:H7 strains with and without the general stress regulatory protein, RpoS, to compete with commercial starter cultures in fermentation systems; and (iii) the survival of E. coli O157:H7 in the yogurt production process. In commercial products inoculated with 103 CFU/ml, E. coli O157:H7 was recovered for up to 12 days in yogurt (pH 4.0), 28 days in sour cream (pH 4.3), and at levels >102 CFU/ml at 35 days in buttermilk (pH 4.1). For the starter culture competition trials, the relative inhibition of E. coli O157:H7 in the experimental fermentation systems was, in decreasing order, thermophilic culture mixture, Lactobacillus delbrueckii subsp. bulgaricus R110 alone, Lactococcus lactis subsp. lactis D280 alone, Lactococcus lactis subsp. cremoris D62 alone, and Streptococcus thermophilus C90 alone showing the least inhibition. Recovery of the rpoS mutant was lower than recovery of its wild-type parent by 72 h or earlier in the presence of individual starter cultures. No E. coli O157:H7 were recovered after the curd formation step in yogurt manufactured with milk inoculated with 105 CFU/ml. Our results show that (i) postprocessing entry of E. coli O157:H7 into fermented dairy products represents a potential health hazard; (ii) commercial starter cultures differ in their ability to reduce E. coli O157:H7 CFU numbers in fermentation systems; and (iii) the RpoS protein appears to most effectively contribute to bacterial survival in the presence of conditions that are moderately lethal to the cell.

Addition to Thermized Milk of Lactococcus lactis subsp. cremoris M104, a Wild, Novel Nisin A–Producing Strain, Replaces the Natural Antilisterial Activity of the Autochthonous Raw Milk Microbiota Reduced by Thermization

2014 ◽  
Vol 77 (8) ◽  
pp. 1289-1297 ◽  
Author(s):  
ALEXANDRA LIANOU ◽  
JOHN SAMELIS
Keyword(s):  
Lactococcus Lactis ◽  
Great Part ◽  
Raw Milk ◽  
Control Treatment ◽  
Lactococcus Lactis Subsp ◽  
Milk Samples ◽  
Bulk Milk ◽  
C 30 ◽  
Sterilized Milk ◽  
Cheese Production

Recent research has shown that mild milk thermization treatments routinely used in traditional Greek cheese production are efficient to inactivate Listeria monocytogenes and other pathogenic or undesirable bacteria, but they also inactivate a great part of the autochthonous antagonistic microbiota of raw milk. Therefore, in this study, the antilisterial activity of raw or thermized (63°C, 30 s) milk in the presence or absence of Lactococcus lactis subsp. cremoris M104, a wild, novel, nisin A–producing (Nis-A+) raw milk isolate, was assessed. Bulk milk samples were taken from a local cheese plant before or after thermization and were inoculated with a five-strain cocktail of L. monocytogenes (approximately 4 log CFU/ml) or with the cocktail, as above, plus the Nis-A+ strain (approximately 6 log CFU/ml) as a bioprotective culture. Heat-sterilized (121°C, 5 min) raw milk inoculated with L. monocytogenes was used as a control treatment. All milk samples were incubated at 37°C for 6 h and then at 18°C for an additional 66 h. L. monocytogenes grew abundantly (>8 log CFU/ml) in heat-sterilized milk, whereas its growth was completely inhibited in all raw milk samples. Conversely, in thermized milk, L. monocytogenes increased by 2 log CFU/ml in the absence of strain M104, whereas its growth was completely inhibited in the presence of strain M104. Furthermore, nisin activity was detected only in milk samples inoculated with strain M104. Thus, postthermal supplementation of thermized bulk milk with bioprotective L. lactis subsp. cremoris cultures replaces the natural antilisterial activity of raw milk reduced by thermization.

scholarly journals Draft Genome Sequences of 11 Lactococcus lactis subsp. cremoris Strains

2017 ◽  
Vol 5 (11) ◽  
Author(s):  
Michiel Wels ◽  
Lennart Backus ◽  
Jos Boekhorst ◽  
Annereinou Dijkstra ◽  
Marke Beerthuyzen ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacterium ◽  
Lactococcus Lactis ◽  
Dairy Products ◽  
Draft Genome ◽  
Genome Sequences ◽  
Content Type ◽  
Lactococcus Lactis Subsp

ABSTRACT The lactic acid bacterium Lactococcus lactis is widely used for the fermentation of dairy products. Here, we present the draft genome sequences of 11 L. lactis subsp. cremoris strains isolated from different environments.

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