Structural characterisation of xyloglucan and xylans present in olive fruit (Olea europaea cv koroneiki)

Hemicellulose-rich fractions obtained from olive fruit were fractionated by anion-exchange chromatography, which resulted in a xyloglucan-rich pool and four xylan-rich pools. Sugar linkage analyses and degradation studies with specific enzymes were performed to obtain information about the structures. The results indicated a xyloglucan in olive fruit with a specific substitution pattern, which is not commonly found in plant cell walls: XXXG-type building units with both arabinosyl and galactosyl residues linked to it. The xylans present in olive fruit were all very low in substitution with mainly 4-O-methyl-glucuronic acid residues. Enzymatic degradation with endo-xylanases resulted in a mixture of neutral and acidic xylo-oligosaccharides. Striking were the identical degradation patterns on HPAEC for all xylan-rich pools while the elution of the pools on DEAE Sepharose differed markedly.