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In vitro degradation of forage chicory ( Cichorium intybus L.) by endopoly‐ galacturonase
Author(s) -
Sun Xuezhao,
Hoskin Simone O,
Andrew Ian G,
Joblin Keith N,
Harris Philip J
Publication year - 2007
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.3045
Subject(s) - cichorium , middle lamella , pectin , rumen , cell wall , polysaccharide , red clover , chemistry , biology , botany , food science , fermentation , biochemistry
BACKGROUND: Leaves of forage chicory break down rapidly in the rumen despite little or no rumination. Because chicory cell walls contain high concentrations of pectin, degradation of leaf midrib and leaf lamina tissues by pectinolytic enzymes was investigated. RESULTS: Treatment with endopolygalacturonase (endo‐PG) degraded fresh intact chicory leaves to particles of less than 1 mm in length and solubilised more than 70% of the dry matter within 16 h. Uronic acids were released more extensively than neutral monosaccharides. In similar treatments, 77% of white clover leaflets and 12% of perennial ryegrass leaf blades were solubilised or broken down to particles with a size of less than 1 mm. The degradation of pectic polysaccharides in chicory midribs was monitored by immunofluorescence labelling with monoclonal antibodies JIM5 and JIM7 which target partially methyl‐esterified epitopes of the homogalacturonan (HG) domain of pectin. Examination by fluorescence microscopy revealed that cell separation in the cortical parenchyma of chicory midrib following endo‐PG treatment was associated with loss of HG from the middle lamella, the corners of intercellular spaces and from the tricellular junctions. CONCLUSION: The results of the current study suggest that one of the main contributions to chicory breakdown in the rumen may be cell separation caused by degradation of HG by pectinolytic enzymes from rumen bacteria. Copyright © 2007 Society of Chemical Industry