Endoglucanase effects on energy consumption in mechanical fibrillation of cellulose fibers into nanocelluloses.
Int J Biol Macromol 2023:125002. [PMID:
37217053 DOI:
10.1016/j.ijbiomac.2023.125002]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Revised: 03/16/2023] [Accepted: 05/19/2023] [Indexed: 05/24/2023]
Abstract
Enzymatic processing is seen as a promising means of moving toward environment-friendly industrial processes such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, the properties that make EG pretreatment effective in the isolation of fibrillated cellulose remain a subject of debate. To address this issue, we considered EGs from four glycosyl hydrolase (GH) families (5, 6, 7 and 12) and investigated the roles of the tri-dimensional structures and catalytic features depending on the presence of a carbohydrate binding module (CBM). By using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNF) using mild enzymatic pretreatment followed by disc ultra-refining. Compared with the control (in the absence of pretreatment), the GH5 and GH12 enzymes (CBM free) reduced the fibrillation energy by approximately 15 %. The most efficient energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. They improved the rheological properties of the CNF suspensions (noting that neither of these EGs released soluble products). Interestingly, while the hydrolytic activity was significant (released soluble products), GH7-CBM did not lead to a reduction in fibrillation energy. Hence, the large molecular weight and wide cleft of GH7-CBM led to soluble sugar release but contributed little to fibrillation. Our findings suggest that the improved fibrillation observed upon EG pretreatment is not a consequence of hydrolytic activity or release of products but mostly related to efficient adsorption on the substrate and modification of the surface viscoelastic (amorphogenesis).
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