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Gel filtration studies of peptide metabolism by rumen microorganisms
Author(s) -
Wallace R John
Publication year - 1992
Publication title -
journal of the science of food and agriculture
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.782
H-Index - 142
eISSN - 1097-0010
pISSN - 0022-5142
DOI - 10.1002/jsfa.2740580204
Subject(s) - hydrolysate , peptide , chromatography , chemistry , sephadex , hydrolysis , casein , rumen , biochemistry , size exclusion chromatography , acetic anhydride , enzyme , fermentation , catalysis
Peptide metabolism by rumen microorganisms was investigated by gel filtration using Sephadex G‐25 with water as eluant. Protein hydrolysates containing a mixture of peptides were used to calibrate the column. Total peptide in each fraction was estimated from its A 206 , and free peptide amino groups were analysed by fluorescamine, thus enabling the average peptide M r to be calculated. Three different protein hydrolysates produced similar, nearly linear, relations between log M r and elution volume for peptides between 300 and 2000 Da. Trypticase, a pancreatic hydrolysate of casein, was metabolised rapidly in rumen fluid in vitro. Hydrolysis appeared to be complete after 6 h, leaving a small residual peptide concentration which persisted up to 24 h, equivalent to about 15% of the original peptide concentration of 2 g litre −1 . Residual peptides from casein hydrolysis were 0.05 g litre −1 at 24 h. Peptides accumulated in rumen fluid of sheep receiving dietary ionophores. Two hours after feeding, the accumulation with monensin appeared to be of peptides of a wide M r range, while tetronasin caused an accumulation mainly of smaller, <570 Da, peptides. Treatment of Trypticase with acetic anhydride afforded 76% protection of its peptides from degradation to ammonia in a 6‐h incubation. When Trypticase was fractionated by gel filtration then acetylated, none of the fractions was protected significantly better than others.