Recovery of galactoglucomannan from wood hydrolysate using regenerated cellulose ultrafiltration membranes

Hemicelluloses show promise as a renewable source of raw material for various industrial processes. In this study, galactoglucomannan was recovered from pressurized hot water extract of spruce-sawdust in two steps using hydrophilic regenerated cellulose ultrafiltration membranes having different molecular weight cut-off values. The first step was concentration of galactoglucomannan (GGM) by ultrafiltration using a flat sheet unit and the second step was purification of the retained galactoglucomannan by diafiltration using reverse osmosis filtered water. The highest GGM retention (88%), purity (63%) and recovery (70%) were achieved with the UC005 membrane (cut-off value 5-kDa) at a volume reduction (VR%) of 86%. The UC010 and UC030 membranes (cut-off values 10- and 30-kDa, respectively) partly separated xylan from GGM. Generally, diafiltration did not improve the purity of the GGM due to overlapping of the GGM and lignin molar mass distributions and the fact that most of free low molar mass lignin had already been removed in the concentration filtration step. However, by diafiltration, partial removal of xylan and complete removal of monosaccharides from the GGM rich concentrate was achieved.