Linked Life Data

12427933

Source:http://linkedlifedata.com/resource/pubmed/id/12427933

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 11
pubmed:dateCreated
2002-11-12
pubmed:abstractText
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 PrtB-negative 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.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Nov
pubmed:issn
1350-0872
pubmed:author
pubmed:issnType
Print
pubmed:volume
148
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3413-21
pubmed:dateRevised
2006-11-15
pubmed:meshHeading
pubmed:year
2002
pubmed:articleTitle
Cell-wall proteinases PrtS and PrtB have a different role in Streptococcus thermophilus/Lactobacillus bulgaricus mixed cultures in milk.
pubmed:affiliation
Unité de Biochimie et Structure des Protéines, INRA, 78352 Jouy-en-Josas Cedex, France.
pubmed:publicationType
Journal Article