Production of cellulose nanofibrils from bleached eucalyptus fibers by hyperthermostable endoglucanase treatment and subsequent microfluidization

A GH5 hyperthermostable endoglucanase from the archaeon Pyrococcus horikoshii (Ph-GH5) and a commercial endoglucanase FR were used to treat bleached eucalyptus pulp (BEP) fibers to produce cellulose nanofibrils (CNFs) through subsequent microfluidization. Enzymatic treatments facilitated CNF production due to the reduced degree of polymerization (DP) of the fibers. SEM imaging indicated that FR reduced fiber DP drastically and resulted in much shorter fibers than with Ph-GH5, even at very low dosages (1 mg protein/g fiber) of FR treatment compared with a high dosage (10 mg protein/g fiber) of Ph-GH5. The fibers treated with FR were much more uniform in length perhaps due to the presence of exoglucanase and beta-glucosidase saccharifying short microfibers into glucose. TEM imaging indicated that Ph-GH5 produced longer and entangled CNFs than FR with the same number of microfluidization passes. However, the CNF diameters were approximately the same for all CNFs from enzyme-treated fibers using both endoglucanases at two dosages (1 or 10 mg protein/g fiber). CNFs produced from BEP fibers without enzymatic treatment showed larger diameters than those with enzymatic treatment.