Microbial community dynamics in thermophilic undefined milk starter cultures.

Model undefined thermophilic starter cultures were produced from raw milk of nine pasta-filata cheesemaking plants using a selective procedure based on pasteurization and incubation at high temperature with the objective of studying the microbial community dynamics and the variability in performances under repeated (7-13) reproduction cycles with backslopping. The traditional culture-dependent approach, based on random isolation and molecular characterization of isolates was coupled to the determination of pH and the evaluation of the ability to produce acid and fermentation metabolites. Moreover, a culture-independent approach based on amplicon-targeted next-generation sequencing was employed.

The microbiota of high-moisture mozzarella cheese produced with different acidification methods.

The microbiota of high-moisture Mozzarella cheese made from cow's milk and produced with different acidification methods was evaluated at the end of refrigerated storage by pyrosequencing of the 16S rRNA gene. The cheeses were clearly separated on the basis of the acidification methods. Cheeses produced with the addition of starters were dominated by Streptococcus thermophilus, but a variety of lactic acid bacteria and spoilage microorganisms appeared at low levels (0.

Genotypic diversity of stress response in Lactobacillus plantarum, Lactobacillus paraplantarum and Lactobacillus pentosus.

Lactobacillus plantarum, Lactobacillus pentosus and Lactobacillus paraplantarum are three closely related species which are widespread in food and non-food environments, and are important as starter bacteria or probiotics. In order to evaluate the phenotypic diversity of stress tolerance in the L. plantarum group and the ability to mount an adaptive heat shock response, the survival of exponential and stationary phase and of heat adapted exponential phase cells of six L.

Inactivation of ccpA and aeration affect growth, metabolite production and stress tolerance in Lactobacillus plantarum WCFS1.

The growth of Lactobacillus plantarum WCFS1 and of its ΔccpA ery mutant, WCFS1-2, was compared in batch fermentations in a complex medium at controlled pH (6.5) and temperature (30°C) with or without aeration, in order to evaluate the effect of ccpA inactivation and aeration on growth, metabolism and stress resistance. Inactivation of ccpA and, to a lesser extent, aeration, significantly affected growth, expression of proteins related to pyruvate metabolism and stress, and tolerance to heat, oxidative and cold/starvation stresses.