Array-based microfibril surface assessment (AMSA): a method for probing surface-exposed polysaccharides on cellulose nanofibres

Small amounts of polysaccharides remaining tightly bound to cellulose microfibrils in the plant cell wall are significant to cell wall architecture and of importance to the rheological properties of plant-derived cellulose nanofibres (CNFs). A method for detecting these polysaccharides is presented. The method, Array-based Microfibril Surface Assessment (AMSA), uses monoclonal antibodies to probe polysaccharides that are exposed on fibrous material. Microfluidised alcohol insoluble residue from sugar beet pulp was used as control and baseline, representing a minimally processed material. To test the utility of AMSA, CNF prepared from sugar beet pulp were analysed. Surprisingly, nanofibrillation did not enhance binding of CBM3a (specific to crystalline cellulose) which indicates that bare cellulose is not easily made. However, nanofibrillation exposed a large amount of unbranched mannan, implying that mannan is closely associated with cellulose in these cell walls. Additional treatment of the CNF suspensions with pectinases removed the majority of homogalacturonan and rhamnogalacturonan I, which caused flocculation of the samples. This highlights the importance of preserving small quantities of these polysaccharides to promote CNF-water interactions and obtain well-dispersed fibres. In conclusion, it is demonstrated how AMSA has a utility in both biotechnological applications involving CNF as well as for exploring plant cell wall architecture. Graphic abstract