From waste to high-value products: Impact of galactoglucomannan purity on selected hydrogel properties

Hydrogels are a hydrophilic network of polymers (usually cross-linked polysaccharides) that are natural or synthetic. Applications of hydrogels are many in the biomedical field. Because of the high water absorption (10 to 200 grams of water per gram of hydrogel), hydrogels have a high degree of flexibility similar to natural human tissue. Human cells can be incorporated into the hydrogel, which in turn can be used to repair damaged tissue. An option is to incorporate drugs in the gels to treat a damaged area by a sustained-release drug-delivery system. Other uses have been in the production of bio-sensors, as absorbent in, e.g. diapers or in the production of contact lenses.Hemicelluloses (in this work galactoglucomannan (GGM)) are a promising renewable raw material for the production of hydrogels. Given their high abundance (constituting up to 25% of the wood cell walls) and current lack of use (usually incinerated together with other biopolymers in the pulp and paper industry), makes this work valuable from an economical and industrial point-of-view.In this work, we examine the possibility to produce hydrogels from GGM extracted from sodium-based spent-sulfite-liquor using a combination of membrane filtration and anti-solvent precipitation. The impact of GGM purity or the addition of lignosulfonates to the cross-linking reaction mixture (in-direct effect of the downstream processing, which affect the overall process economy) on the mechanical, thermal and chemical properties of the hydrogel have been examined and evaluated