STRUCTURAL FEATURES OF GALACTANS FROM FLAX FIBERS

Successive extraction of mechanically-isolated flax fibres with ethylene-diamine-tetraacetic acid partially neutralized with NAOH EDTA-Na-2 and NaOH solubilized about 25% of the mass of fibres. The cation exchange capacity (CEC) of the fibres decreased from 0.100 +/- 0.025 meg g(-1) to 0.035 +/- 0.015 meg g(-1) after EDTA-Na-2 extraction and then was reduced to virtually nil by extraction with NaOH. This final reduction in CEC by alkali was accompanied by the extraction of small charge molecules, notably phenolic acids. These may influence the binding selectivity of the fibre towards monovalent cations. Polymers solubilized by this extraction procedure included two main types of galactans; the first type consisted of beta-1-->4 galactans attached to a rhamnogalacturonan I-like polymer and the second type was beta-1-->3, beta-1-->6 linked galactans attached to proteins in some unknown manner. In addition, some beta-1-->3 glucan, beta-1-->4 glucan and glucomannan-like polymers were detected.