Mechanistic investigation of the effect of endoglucanases related to pulp refining

Abstract

Endoglucanases are increasingly being touted as the ultimate solution for reducing energy consumption during the refining process in the pulp and paper industry. However, due to the high variety of endoglucanases in different enzyme formulations, these perform heterogeneously when applied to different pulps. In this study, the effect of four endoglucanases on softwood and hardwood pulp was studied using confocal laser scanning microscopy (CLSM) after addition of fluorescently labelled carbohydrate binding modules (CBMs). Nuclear magnetic resonance (NMR) analysis and high-performance liquid chromatography quantification of released oligo- and monosaccharides was performed for in-depth mechanistical investigation. Changes in the crystallinity levels caused by enzymatic degradation of amorphous regions were monitored by incubation with two different CBMs from Caldicellulosiruptor bescii and from Thermobifida fusca with high preference to either amorphous or crystalline regions of cellulose, respectively. When dosed at identical activity on the endoglucanase specific CellG5 substrate, CLSM analysis indicated the highest decrease of amorphous regions for those endoglucanases which were also most active in laboratory refining trials and which released highest amounts of cellooligomers from pulp. Using 13C-NMR analysis, an increase in para-crystalline cellulose caused by enzyme application was observed. Release of reducing sugars was determined at identical CellG5 dosage, indicating a high variance between the enzymes, especially when complex enzyme formulations were used. Scanning electron microscopy images were obtained for visualization of the endoglucanase activity. The results of mechanistical studies indicate that reduction of amorphous moieties of pulp by endoglucanases is especially beneficial for the refining process.

Micro-/Nanofibrillated Cellulose-Based Coating Formulations: A Solution for Improving Paper Printing Quality

“…Therefore, ink holdout properties were particularly enhanced by m-MFC [8]. Although more research is still necessary to fully understand the effects of mechanical stress and endoglucanase-mediated hydrolysis on cellulose, it is generally accepted that the latter targets the amorphous regions [26,27]. Mechanical stress tends to break polymer chains at the middle and to increase their reactivity [28], besides disrupting the structure of the fiber, and thus the higher hydrophilicity that m-MFC produced could be explained by the more severe loss of supramolecular order during the pre-treatment [29].…”

Reduction of fines in recycled paper white water via cellulase enzymes

“…Cellulase enzymes have mainly been used directly in pulp for achieving higher drainage with potentially improved paper mechanical properties (Maximino et al 2011;Kim et al 2017). Endoglucanase activity can effectively catalyze hydrolysis of crystalline and amorphous structure of cellulose and reduce the refining energy (Nagl et al 2022). Kamaya (1996) showed that commercial cellulase from Trichoderma reesei with dominant endoglucanase activity can boost dewatering properties and reduce the refining energy in bleached kraft pulp.…”