Enzymically attaching oligosaccharide-linked 'cargoes' to cellulose and other commercial polysaccharides via stable covalent bonds

The Equisetum enzyme hetero-trans-beta-glucanase (HTG) covalently grafts native plant cellulose (donor-substrate) to xyloglucan (acceptor-substrate), potentially offering a novel 'green' method of cellulose functionalisation. However, the range of cellulosic and non-cellulosic donor substrates that can be utilised by HTG is unknown, limiting our insight into its biotechnological potential. Herewe showthat HTG binds all celluloses tested (papers, tissues, hydrogels, bacterial cellulose) to radioactively- or fluorescently-labelled xyloglucan-heptasaccharide (XXXGol; acceptor-substrate). Glycol-chitin, glycol-chitosan and chitosan also acted as donor substrates but less effectively than cellulose. Cellulose-XXXGol conjugateswere formed throughout the volume of a block of hydrogel, demonstrating penetration. Plant-derived celluloses (cellulose I beta) became more effective donor-substrates after 'mercerisation' in >= 3 M NaOH; the opposite was true for bacterial cellulose I alpha. Cellulose-XXXGol bonds resisted boiling 6 M NaOH, demonstrating strong glycosidic bonding. In conclusion, HTG stably grafts native and processed celluloses to xyloglucan-oligosaccharides, whichmay carry valuable 'cargoes', exemplified by sulphorhodamine. We thus demonstrate HTG's biotechnological potential tomodify various cellulose-based substrates such as textiles, pulps, papers, packaging, sanitary products and hydrogels. (C) 2020 Elsevier B.V. All rights reserved.