Increasing pulp reactivity and thermoformability by combined ionic liquid and enzyme treatments: Screening of optimal ionic liquid – enzyme combinations

In order to allow the preparation of new fibre-based products, it is a key challenge to find methods that increase the reactivity of fibre materials, while still maintaining their mechanical properties. In our current work, we have been looking into a new processing concept, which involves the swelling of fibre surfaces by treatment in ionic liquids (ILs), with a subsequent enzymatic modification step. ILs dissolve cellulose, but adding water to them in a suitable proportion will instead lead to cellulose swelling. While the IL treatment increases the fibre surface accessibility for enzymes, the use of hydrolytic enzymes (glycosyl hydrolases, GHs), e.g. endoglucanases, is anticipated to increase the fibre surface “hairiness” and thus fibre reactivity. Xylanases similarly affect the xylan components of the fibres. Cellulose-swelling ILs inactivate GHs, why the first step in our research was to screen for suitable combinations of GHs and cellulose-swelling ILs. A screening protocol was set up for this task, and nearly 20 endoglucanases and xylanases were screened in two rounds with 15 and 40 % (w/w) solutions of seven different ILs. In this study, several potential GH+IL combinations were found, in which > 60 % of relative enzyme activity was retained in 40 % IL.