Ultrastructural Localisation of Glucomannan in Kraft Pulp Fibres

Summary The localisation of glucomannan on the surface of Norway spruce kraft pulp fibres with varying glucomannan (GM) contents (10.3 and 3.8%) was studied using immunogold labelling, rapid freeze deep etching (RFDE) followed by metal replication and transmission electron microscopy (TEM). The ultrastructure of P, S1 and S2 of pulp fibres with low hemicellulose content tended to be more compact than that of pulp fibres with high hemicellulose content, suggesting aggregation of cellulose microfibrils upon hemicellulose removal. The degree of immunogold labelling visualised as globular structures was similar for the two pulps, despite the large difference in total glucomannan content. Thus, no correlation between the bulk and surface contents of glucomannan was found. The globular structures were heterogeneously located along the cellulose macrofibrils (fibril aggregates) and their frequency varied greatly within and between TEM micrographs.