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Stronger cellulose microfibril network structure through the expression of cellulose-binding modules in plant primary cell walls

Butchosa, Núria, Leijon, Felicia, Bulone, Vincent, Zhou, Qi
Cellulose 2019 v.26 no.5 pp. 3083-3094
Clostridium thermocellum, atomic force microscopy, cell suspension culture, cell walls, cellulose, cellulose microfibrils, deformation, glycosidases, hydrolysis, nanocrystals, protein subunits, sonication, sulfuric acid, tensile strength, tobacco, transmission electron microscopy
Cellulose-binding modules (CBMs) are non-catalytic domains typically occurring in glycoside hydrolases. Their specific interaction with diverse polysaccharides assists hydrolysis by the catalytic subunits. In this work, we have exploited the interactions between a CBM from family 3 (CBM3) and cell wall polysaccharides to alter the structure and mechanical properties of cellulose microfibrils from BY-2 tobacco cell suspension cultures. A CBM3 from Clostridium thermocellum was overexpressed in the cells using Agrobacterium-mediated transformation. Water suspensions of cellulose microfibrils were prepared by the removal of the non-cellulosic components of the primary cell walls, followed by mild disintegration using sonication. The morphology of the microfibrils was characterized by transmission electron microscopy and atomic force microscopy. These cellulose microfibrils were further hydrolyzed with 64 wt% sulfuric acid to produce cellulose nanocrystals (CNCs). The average length of CNCs prepared from the CBM3-transformed cells was 201 nm, higher than that from the wild-type cells (122 nm). In addition, the mechanical properties and deformation mechanism of nanopapers prepared from suspensions of cellulose microfibrils were investigated. The nanopapers obtained from the CBM3-transformed cells exhibited enhanced tensile strength and work of fracture, 40% and 128% higher than those prepared from wild-type tobacco cells, respectively.