No abstract

No abstract

No abstract

No abstract

Enzymatic hydrolysis of sugar-beet pulp, and subsequent isolation of feruloylated oligosaccharides, has shown that ferulic acid groups are ester-linked mainly on O-2 of arabinose residues and on O-6 of galactose residues in the pectin side-chains. After saponiücation of sugar-beet pulp enzymatic digests, dehydrodiferulic acids (0.14% , w/w) have also been identiüed and characterised as 8-5º, 5-5º, 8-8º and 8-O-4º isomers, suggesting that covalent cross-linking of pectic polysaccharides through diferulic bridges occurs in sugar-beet pulp. Feruloylated oligosaccharides from the side-chains of heteroxylans have been isolated from maize bran by acid hydrolysis. Ferulic acid is esteriüed on O-5 of arabinofuranose residues. 8-8º, 8-5º, 8-O-4º and 5-5º coupled dimers, which represent 2.5% (w/w) of the bran, have also been detected. It has been calculated that, in the cell wall, each heteroxylan macromolecule bore ¿75 esteriüed ferulic acid groups and could be cross-linked through ¿30 diferulic bridges. This result suggests a high degree of cross-linking of heteroxylans chains through ferulic acid in maize bran cell walls. 1999 Society of Chemical Industry (

No abstract

No abstract

The structure of arabinan and galactan domains in association with cellulose microfibrils was investigated using enzymatic and alkali degradation procedures. Sugar beet and potato cell wall residues (called 'natural' composites), rich in pectic neutral sugar side chains and cellulose, as well as 'artificial' composites, created by in vitro adsorption of arabinan and galactan side chains onto primary cell wall cellulose, were studied. These composites were sequentially treated with enzymes specific for pectic side chains and hot alkali. The degradation approach used showed that most of the arabinan and galactan side chains are in strong interaction with cellulose and are not hydrolysed by pectic side chain-degrading enzymes. It seems unlikely that isolated arabinan and galactan chains are able to tether adjacent microfibrils. However, cellulose microfibrils may be tethered by different pectic side chains belonging to the same pectic macromolecule.