Quantitative assessment of xylan distribution across the secondary cell wall layers of Eucalyptus dissolving pulp fibres

Abstract

A quantitative method has been developed for assessment of the distribution of xylan across the secondary cell wall layers of Eucalyptus dissolving pulp fibres by means of a carbohydrate binding module (CBM), CtCBM6, in combination with transmission electron microscopy (TEM). To ensure reproducibility and to minimise nonspecific labelling, various parameters were optimised, namely the size of the gold colloid marker, CtCBM6 concentration, and the selection of buffer solutions. The method was replicated on processed Eucalyptus fibres containing different xylan contents. Reproducible xylan counts and distributions across the secondary cell wall layers were obtained for unbleached and bleached Eucalyptus fibres. The xylan distribution pattern across the cell wall layers S1, S2 and S3 was similar, but the S1 and S3 layers contained after bleaching more xylan than the S2 layer. The technique has a wide range of applications in basic wood research as well as in the analysis of technological processes.