Abstract text: Hetero-trans-β-glucanase (HTG), sourced from a botanical ‘trilobite’, Equisetum, covalently grafts cellulose to (oligo)xyloglucans (XGOs), creating hybrid cellulose–xyloglucan conjugates. Excitingly, the XGOs employed can be carrying a desired functional ‘cargo’, e.g. a fluorophore, hydrophobic moiety, pH indicator, xenobiotic etc. Here we will present (a) successful methodologies for synthesizing novel cargo-loaded substrates and (b) HTG’s potential for modifying cellulose in vivo and industrially.

The novel ‘cargoes’ include a hydrophobic group (octyl or hexadecyl); a bifunctional linker (N,N´-dimethylethylenediamine) which dimerises XGOs; and coloured dyes.

The HTG used was either a crude Equisetum extract or a heterologously-expressed Pichia product. Sugar-beet pulp (SBP), a cellulose-rich by-product of the sucrose industry, was treated with HTG plus a cargo-bearing XGO. The treatment improved the mechanical strength, viscosity and water-absorption/repellency of SBP. The bifunctional ‘linker’ may enable HTG to covalently interlink cellulose chains. Our observations also highlight potential roles for HTG in wall-strengthening in vivo.

We conclude that HTG, together with novel ‘cargo’-bearing XGOs, has unique potential in functionalising and potentially cross-linking cellulose. It opens new ‘green’ strategies for biotechnologically enhancing cellulose. It may reveal an unexplored mechanism by which Equisetum (the most evolutionarily isolated plant genus) has acquired the ability to strengthen its cell walls.