Oligopeptides are the main source of nitrogen for Lactococcus lactis during growth in milk.
Appl Environ Microbiol
; 61(8): 3024-30, 1995 Aug.
Article
em En
| MEDLINE
| ID: mdl-7487034
ABSTRACT
The consumption of amino acids and peptides was monitored during growth in milk of proteinase-positive (Prt+) and -negative (Prt-) strains of Lactococcus lactis. The Prt- strains showed monophasic exponential growth, while the Prt+ strains grew in two phases. The first growth phases of the Prt+ and Prt- strains were in same, and no hydrolysis of casein was observed. Also, the levels of consumption of amino acids and peptides in the Prt+ and Prt- strains were similar. At the end of this growth phase, not all free amino acids and peptides were used, indicating that the remaining free amino acids and peptides were unable to sustain growth. The consumption of free amino acids was very low (about 5 mg/liter), suggesting that these nitrogen sources play only a minor role in growth. Oligopeptide transport-deficient strains (Opp-) of L. lactis were unable to utilize oligopeptides and grew poorly in milk. However, a di- and tripeptide transport-deficient strain (DtpT-) grew exactly like the wild type (Opp+ Dtpt+) did. These observations indicate that oligopeptides represent the main nitrogen source for growth in milk during the first growth phase. In the second phase of growth of Prt+ strains, milk proteins are hydrolyzed to peptides by the proteinase. Several of the oligopeptides formed are taken up and hydrolyzed internally by peptidases to amino acids, several of which are subsequently released into the medium (see also E.R.S. Kunji, A. Hagting, C.J. De Vries, V. Juillard, A.J. Haandrikman, B. Poolman, and W.N. Konings, J. Biol. Chem. 2701569-1574, 1995).(ABSTRACT TRUNCATED AT 250 WORDS)
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oligopeptídeos
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Lactococcus lactis
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Leite
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Nitrogênio
Limite:
Animals
Idioma:
En
Revista:
Appl Environ Microbiol
Ano de publicação:
1995
Tipo de documento:
Article
País de afiliação:
França