INVESTIGATION OF THE OCCURRENCE OF XYLAN-XYLOGLUCAN COMPLEXES IN THE CELL-WALLS OF OLIVE PULP (OLEA-EUROPAEA)

Previously we reported the possible occurrence of a complex containing glucuronoxylan and xyloglucan in the cell walls of olive pulp. In ord er to investigate the nature of this complex, the 1 M KOH (1 degrees C )-soluble polysaccharides in which it was prevalent, were separated by graded ethanol precipitation followed by anion-exchange chromatograph y. A slightly acidic fraction was obtained and, by methylation analysi s, glycosidic linkages typical of both xylan and xyloglucan were detec ted. Two distinct populations of the xylan-xyloglucan complexes were r esolved by gel-filtration chromatography (2000 and 100 kDa) and the st ructural features were determined by methylation analysis. Cross-linki ng of the xylan-xyloglucan moieties was investigated by digestion of t he xylan component with a purified, specific, endoxylanase. Although o nly the xylan element was digested, as verified by methylation analysi s, the molecular weight of the xyloglucan moiety was also reduced. Thi s confirmed that the xylan and xyloglucan moieties were strongly attac hed. The occurrence and structure of the xylan-xyloglucan complexes in the olive pulp cell walls is discussed.