Introduction
The high carbon footprint of materials production for food packaging and biomedicine is driving a strong pursuit for novel materials with tailored properties, able to meet functional requirements with a minimal environmental impact. Lignin sourced from the side-stream of the pulp-and-paper industry is emerging as a promising alternative to fossil-based polymers. However, tailoring lignin properties for applications remains a challenge. Herein, a novel hemicellulose-rich, high-molecular weight lignosulphonate (WOODMER® by Ecohelix, abbreviated as EH) has been developed for food-packaging and drug delivery.
Methods
EH was produced starting from the side-stream biomass of a sulphite pulping process. Membrane filtration was used to isolate and purify the polymeric mixture, which was further crosslinked by enzymatic treatment using natural laccase (patented technology). EH was characterized in terms of composition and molecular weight (MW). As an example in food packaging, EH was combined with polyethylenimine (PEI) or chitosan (CH) using a layer-by-layer (LbL) technology to yield sustainable coatings of polyethylene (PE) with improved barrier properties. As an example in drug delivery, EH was combined with PEI or CH to form hydrogels able to entrap and release a model aromatic drug.
Results
The composition analysis of EH revealed a higher hemicellulose content (up to 11 times), a 3-fold increase in MW (30 kDa), and 1.5 times more aliphatic OH groups (by P-NMR) compared to traditional lignosulphonate. In the LbL study, surface chemistry techniques (QCM-D, SPAR) showed homogeneous multilayer formation between EH and PEI or CH. Light barrier properties of coated PE increased > 5 times compared to PE, and oxygen barrier properties improved up to 94%. In the drug delivery study, hydrogels showed high drug encapsulation (up to 98%) and a controlled release profile (up to 7 mg/g of dry hydrogel) in an in-vivo simulated condition of oral administration.
Conclusions
We defined the conditions to produce a novel hemicellulose-rich lignosulphonate with reproducible properties and use it for sustainable applications in food-packaging and drug delivery.

Michael Reid

KTH Royal Institute of Technology

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