Browsing by Author "Arantes, Valdeir"

Now showing 1 - 2 of 2
  • No Thumbnail Available
    Item
    Endoglucanase effects on energy consumption in the mechanical fibrillation of cellulose fibers into nanocelluloses
    (Elsevier, 2023-07-15) Berto, Gabriela L.; Mattos, Bruno D.; Velasco, Josman; Zhao, Bin; Segato, Fernando; Rojas, Orlando J.; Arantes, Valdeir; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; Universidade de São Paulo
    Enzymatic processing is considered a promising approach for advancing environmentally friendly industrial processes, such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, there is ongoing debate regarding the specific properties that make EG pretreatment effective in isolating fibrillated cellulose. To address this issue, we investigated EGs from four glycosyl hydrolase (GH) families (5, 6, 7, and 12) and examined the roles of the three-dimensional structure and catalytic features, with a focus on the presence of a carbohydrate binding module (CBM). Using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNFs) through mild enzymatic pretreatment, followed by disc ultra-refining. Comparing the results with the control (without pretreatment), we observed that GH5 and GH12 enzymes (without CBM) reduced fibrillation energy by approximately 15 %. The most significant energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. Notably, these CBM-linked EGs improved the rheological properties of CNF suspensions without releasing soluble products. In contrast, GH7-CBM exhibited significant hydrolytic activity, resulting in the release of soluble products, but did not contribute to a reduction in fibrillation energy. This discrepancy can be attributed to the large molecular weight and wide cleft of GH7-CBM, which led to the release of soluble sugars but had little impact on fibrillation. Our findings suggest that the improved fibrillation observed with EG pretreatment is primarily driven by efficient enzyme adsorption on the substrate and modification of the surface viscoelasticity (amorphogenesis), rather than hydrolytic activity or release of products.
  • No Thumbnail Available
    Item
    Single-step fiber pretreatment with monocomponent endoglucanase : Defibrillation energy and cellulose nanofibril quality
    (AMERICAN CHEMICAL SOCIETY, 2021-02-08) Berto, Gabriela L.; Mattos, Bruno D.; Rojas, Orlando J.; Arantes, Valdeir; Department of Bioproducts and Biosystems; Bio-based Colloids and Materials; Universidade de São Paulo
    The combination of enzymatic pretreatment of cellulose fibers followed by mechanical defibrillation has become a green and low-energy route to obtain cellulose nanofibrils (CNF). However, the variability in the properties of the as-produced CNF remains a major challenge that needs to be addressed for any application to be realized. Herein, we study the effect of monocomponent endoglucanase (EG) on the energy consumed in defibrillation as well as the physical properties of the obtained CNF. This single-step enzymatic pretreatment (0.5−25 EGU/g cellulose fibers for 1−3 h) reduces the defibrillation energy (by up to 50%) at nearly 100% yield to obtain CNF of a similar morphology, size, and crystallinity compared to CNF obtained in the absence of pretreatment. Under mild conditions (5.6 EGU/g for 1 h), aiming to minimize energy consumption while preserving rheological properties, EG pretreatment increased the water retention value, reduced the molecular weight, and promoted structural surface modification (amorphogenesis), without significant cellulose solubilization. In addition, the carbohydrate binding module of the EG was found to improve the interaction of the catalytic core with the substrate. The combination of the factors considered here boosts the effect of the enzyme even if used at low loadings, facilitating high-yield, more sustainable production of CNF.