Use of cellulases and recombinant cellulose binding domains for refining TCF kraft pulp

Abstract

The modular endoglucanase Cel9B from Paenibacillus barcinonensis is a highly efficient biocatalyst, which expedites pulp refining and reduces the associated energy costs as a result. In this work, we set out to identify the specific structural domain or domains responsible for the action of this enzyme on cellulose fibre surfaces with a view to facilitating the development of new cellulases for optimum biorefining. Using the recombinant enzymes GH9-CBD3c, Fn3-CBD3b, and CBD3b, which are truncated forms of Cel9B, allowed us to assess the individual effects of the catalytic, cellulose binding, and fibronectin-like domains of the enzyme on the refining of TCF kraft pulp from Eucalyptus globulus. Based on the physico-mechanical properties obtained, the truncated form containing the catalytic domain (GH9-CBD3c) has a strong effect on fibre morphology. Comparing its effect with that of the whole cellulase (Cel9B) revealed that the truncated enzyme contributes to increasing paper strength through improved tensile strength and burst strength and also that the truncated form is more effective than the whole enzyme in improving tear resistance. Therefore, the catalytic domain of Cel9B has biorefining action on pulp. Although cellulose binding domains (CBDs) are less efficient toward pulp refining, evidence obtained in this work suggests that CBD3b alters fibre surfaces and influences paper properties as a result.

Enzymatic approaches in paper industry for pulp refining and biofilm control

“…Cellulases act on the surface and inner layers of cellulose fibers in an efficient enough way to allow the production of special paper with reduced energy consumption. Cellulase effects on fiber morphology lead to improved fiber-fiber bonding in the refining process and hence to increased fiber cohesion in the final paper (Cadena 2010;Kaur 2010;Kuhad 2011;Luo 2011;Ponce and Perez 2002).…”

“…This association is named laccase mediator system (LSM). In these socalled LMS, the mediator is first oxidized by the laccase and then diffuses into the cell wall, oxidizing lignin inaccessible to laccase (Cadena 2010;Camarero 2007;Riva 2006: Widsten andKandelbauer 2008).…”

“…The study performed by Cadena (2010), using Cel9B and the truncated forms, which contained various combinations of the functional domains of Cel9B GH9-CBD3c, Fn3-CBD3b, and CBD3b from Paenibacillus barcinonensis, on total chlorine free bleached (TCF) pulp from Eucalyptus globulus (consistency 10%) also evaluates the enzyme effects on refining. The application of endoglucanase Cel9B was found to accelerate the mechanical refining of pulp in a PFI mill and also to decrease its CSF and to increase its WRV.…”

Comparative evaluation of the action of two different endoglucanases. Part I: On a fully bleached, commercial acid sulfite dissolving pulp

“…The treatments were named as follows: CCE, K, K_CCE, B120, CCE_B120, B120_CCE, 164 Pulp degradation can also be assessed via the number of scissions in the cellulose chain 174 (CS), which is defined mathematically as (Bouchard et al 2000): 175…”

Approaching a Low-Cost Production of Cellulose Nanofibers for Papermaking Applications

“…The application of dry-strength additives such as cationic polyelectrolytes is extensively used as method to improve strength in paper and drainage rate. The use of enzymes, particularly cellulases, on papermaking pulps has also been studied as a green approach for reducing beating (García et al 2002;Cadena et al 2010) or eliminating it altogether (González et al 2013).…”