Towards a better understanding of synergistic enzyme effects during refining of cellulose fibers

Refining of cellulose fibers is essential for reaching desired paper properties, yet highly energy demanding. Enzymes like endoglucanases (e.g. EndoC) are increasingly used to reduce energy consumption during pulp refining. However, prediction of the enzyme effect is still a major concern, considering the high variety of commercially available enzyme formulations, containing a range of different enzymes. In this study, synergisms of xylanases and β-glucosidases in combination with endoglucanases purified from enzyme formulations were studied and related to their refining performance. Size exclusion chromatography with multi-angle laser light scattering (SEC-MALLS) of carboxymethylcellulose revealed that a narrow size distribution and a high reduction in molecular weight are beneficial characteristics for refining. SEC-MALLS of hardwood pulp resulted in pronounced formation of low molecular weight fractions (log MW 4.3) for most efficient refining enzymes. Application of enzyme formulations and combinations of endoglucanase EndoC with β-glucosidase or xylanase using Fourier-transform infrared spectroscopy (FTIR) revealed synergistic effects that promoted degradation of amorphous parts of cellulose. Laboratory refining trials on hardwood pulp confirmed the increase in degree of refining and tensile index after addition of xylanase and β-glucosidase. Surface plasmon resonance (SPR) analysis resulted in strong binding of endoglucanases to regenerated cellulose, which correlated to refining performance.