Production and Characterization of Cellulose Nanocrystals from Eucalyptus Dissolving Pulp Using Endoglucanases from Myceliophthora thermophila

Abstract

Endoglucanase (EG) is a key enzyme during enzymatic preparation of cellulose nanocrystals (CNCs). Myceliophthora thermophila is a thermophilic fungus that has thermal properties and a high secretion of endoglucanases (EGs), and could serve as potential sources of EGs for the preparation of CNCs. In this work, four different GH families (GH5, GH7, GH12, and GH45) of EGs from M. thermophila were expressed and purified, and their enzymatic characteristics and feasibility of application in CNC preparation were investigated. It was shown that the MtEG5A from M. thermophila has good potential in the enzymatic preparation of CNCs using eucalyptus dissolving pulp as feedstock. It was also observed that there was a synergistic effect between the MtEG5A and other MtEGs in the preparation of CNCs, which improved the yield and properties of CNCs obtained by enzymatic hydrolysis. This study provides a reference for understanding the enzymatic characteristics of different families of EGs from M. thermophile and their potential application in nanocellulose production.

Keywords: Myceliophthora thermophila; cellulose nanocrystals; endoglucanases; enzymatic characteristics; enzymatic hydrolysis; eucalyptus dissolving pulp.

Figure 1

Effect of temperature (a) and pH (b) on the activity of different endoglucanases.

Figure 2

DLS analysis (a) and yield (b) of CNCs obtained by enzymatic hydrolysis of EDP with different EGs.

Figure 3

TEM images of CNCs prepared by enzymatic hydrolysis of EDP using MtEG5A (a), (5+7) (b), (5+12) (c), and (5+7+45) (d).

Figure 4

XRD pattern (a) and crystallinity (b) of CNCs prepared by enzymatic hydrolysis with MtEG5A alone and different EG combinations.

Figure 5

Thermal stability analysis of the CNCs: TGA curves (a); DTG curves (b).