L'état des connaissances en matière de nutrition des bactéries lactiques

Desmazeaud, M.

doi:10.1051/lait:1983629-63018

Cited by 60 publications

(20 citation statements)

References 9 publications

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“…bulgaricus does not grow ; S. thermophilus is thus responsible for this first acidification, as first observed by Pette & Lolkema (1950c). The preferential growth of S. thermophilus can be explained first by the fact that S. thermophilus has fewer nutritional requirements than lactobacilli in milk (Desmazeaud, 1983). In particular, S. thermophilus requires few amino acids and is capable of synthesizing branched-chain amino acids ; its growth can probably be supported by free amino acids and peptides present in milk, as previously demonstrated in pure culture, regardless of the presence of PrtS (Letort et al, 2002).…”

Section: Lb Bulgaricus and Effect On Acidificationmentioning

confidence: 81%

Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk

2002

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The manufacture of yoghurt relies on the simultaneous utilization of two starters : Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus (Lb. bulgaricus). A protocooperation usually takes place between the two species, which often results in enhanced milk acidification and aroma formation compared to pure cultures. Cell-wall proteinases of Lactococcus lactis and lactobacilli have been shown to be essential to growth in milk in pure cultures. In this study, the role of proteinases PrtS from S. thermophilus and PrtB from Lb. bulgaricus in bacterial growth in milk was evaluated ; a negative mutant for the prtS gene of S. thermophilus CNRZ 385 was constructed for this purpose. Pure cultures of S. thermophilus CNRZ 385 and its PrtS-negative mutant were made in milk as well as mixed cultures of S. thermophilus and Lb. bulgaricus : S. thermophilus CNRZ 385 or its PrtS-negative mutant was associated with several strains of Lb. bulgaricus, including a PrtBnegative strain. The pH and growth of bacterial populations of the resulting mixed cultures were followed, and the Lactobacillus strain was found to influence both the extent of the benefit of Lb. bulgaricus/S. thermophilus association on milk acidification and the magnitude of S. thermophilus population dominance at the end of fermentation. In all mixed cultures, the sequential growth of S. thermophilus then of Lb. bulgarius and finally of both bacteria was observed. Although proteinase PrtS was essential to S. thermophilus growth in milk in pure culture, it had no effect on bacterial growth and thus on the final pH of mixed cultures in the presence of PrtB. In contrast, proteinase PrtB was necessary for the growth of S. thermophilus, and its absence resulted in a higher final pH. From these results, a model of growth of both bacteria in mixed cultures in milk is proposed.

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Section: Lb Bulgaricus and Effect On Acidificationmentioning

confidence: 81%

Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk

2002

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“…Le report à 2 o C entraîne une augmentation du niveau de lipolyse liée en grande partie à l'activité lipolytique des germes psychrotrophes [2]. Un effet inhibiteur des acides gras libres sur les ferments lactiques a été observé dans le cas du lait de vache [3], mais nos résultats obtenus sur le lait de chèvre ne permettent pas de conclure à un tel effet.…”

Section: Effet Des Traitements Thermiquesunclassified

Aptitude du lait de chèvre à l'acidification par les ferments lactiques - Facteurs de variation liés à la composition du lait

Masle¹,

Morgan²

2001

Lait

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-Compositional factors involved in the variable acidification capacity of goat milk by lactic starters. This study was designed to define the factors involved in the variable acidification capacity of goat milk by lactic starters. Acidification capacity and compositional parameters of 28 goat milk samples were determined. The influences of the period of production and of some technological treatments (cold storage and heating) were also investigated. The results point out the influence of milk composition, and notably the role of the buffering components such as proteins and minerals. An improved activity of lactic starters is observed in milks with a high level of proteins and minerals. The lactation period, through its effect on the protein concentration, affects the acidification capacity of goat milk. Cold storage does not exert any major influence on the acidification process. However, the results indicate that heating of milk lead to an improved activity of lactic starters at the beginning of the acidification period.goat milk / acidification / lactic starter / composition

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“…The thermophilic bacterium S. thermophilus requires fewer amino acids than lactococci and lactobacilli (9). Only glutamine and glutamic acid, along with the sulfur amino acids, are essential for all of the strains that have been tested (3, 28; data not shown).…”

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confidence: 99%

Branched-Chain Amino Acid Biosynthesis Is Essential for Optimal Growth of Streptococcus thermophilus in Milk

Garault

Letort

Juillard

et al. 2000

Appl Environ Microbiol

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Lactic acid bacteria are nutritionally demanding bacteria which need, among other things, amino acids for optimal growth. We identified the branched-chain amino acid (BCAA) biosynthesis pathway as an essential pathway for optimal growth of Streptococcus thermophilus in milk. Through random insertional mutagenesis, we isolated and characterized two mutants for which growth in milk is affected as a consequence of ilvB and ilvC gene interruptions. This situation demonstrates that the BCAA biosynthesis pathway is active in S. thermophilus. BCAA biosynthesis is necessary but not sufficient for optimal growth of S. thermophilus and is subject to retro-inhibition processes. The specificity of the BCAA biosynthesis pathway in S. thermophilus lies in the independent transcription of the ilvC gene encoding a keto acid reductoisomerase acting on acetolactate at the junction of the BCAA and acetoin biosynthesis pathways. The possible advantages for S. thermophilus of keeping this biosynthesis pathway active could be linked either to adaptation of the organism to milk, which is different than that of other dairy bacteria, or to the role of the pathway in maintaining the internal pH.

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L'état des connaissances en matière de nutrition des bactéries lactiques

Cited by 60 publications

References 9 publications

Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk

Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk

Aptitude du lait de chèvre à l'acidification par les ferments lactiques - Facteurs de variation liés à la composition du lait

Branched-Chain Amino Acid Biosynthesis Is Essential for Optimal Growth of Streptococcus thermophilus in Milk

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