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Using fractionation, cellulose fibres can be delaminated into cellulose nanofibers and have attracted much attention due to their excellent properties. Nevertheless, their production remains limited because of the high energy required for the fibrillation of lignocellulose. In order to reduce the energy consumption, two main strategies are presently employed: the pretreatment of the fibers by cellulases, which usually results in variable quality and yield of nanofibers; and oxidation, which produces large quantities of toxic effluents.

We have investigated new strategies as a pretreatment for their cellulose fractionation by a new type of enzyme, “lytic polysaccharide monooxygenases” (LPMO), which have demonstrated the ability to cleave glycosidic bonds by oxidation instead of hydrolysis performed by cellulases. This innovative catalysis may therefore be used as a pretreatment and/or as a modification step of cellulose fibers for producing nanocelluloses.

By studying the action of fungal LPMOs on paper fibers obtained by the Kraft procedure, we have demonstrated the disruption of the cellulose fiber arrangement. NMR studies have revealed a modification of the accessible amorphous and inaccessible surfaces. A model for the organization of the different regions of cellulose crystalline, amorphous, para-crystalline, accessible and inaccessible, has been proposed, showing that the crystalline regions become less ordered. The crystallinity values and the lateral dimensions of individual fibrils and aggregates show an increase in the porosity upon the action of LPMOs. On the other hand, molar mass distribution of the Kraft fibers shows the decrease of molar mass upon the LPMO enzymatic treatment. Nevertheless, this decrease is limited compared to other procedures of fabrication of nanocelluloses, which suggests a good preservation of the mechanical properties of the fibers.

For the first time, these results show the effect of LPMO enzymes on insoluble cellulose. The obtained results are promising since the action of LPMO enzymes may be used as a new strategy for the preparation of cellulose nanofibers. Current research is focused on the study of the action of LPMOs on other types of cellulose/hemicellulose substrates (xyloglucan, xylan).

Partners

• INRA BIA et INRA-AMU BBF
• A collaboration has been established with the CTP and the FCBA of Grenoble (France) and with the wood chemistry laboratory of the University of Hamburg (Germany).

Publications

A patent was filed in June 2015 : Cathala B., Villares A., Moreau C., Berrin J.G. FR 2015/ 1555049 Procédé pour la fabrication de nanocelluloses à partir d'un substrat cellulosique (3 Juin 2015)

Lytic polysaccharide monooxygenases disrupt the cellulose fibers structure, Villares A., Moreau C., Bennati-Granier C., Garajova S., Foucat L., Falourd X., Saake B., Berrin J.G., Cathala B., Scientific Reports, 2017, 7, 40262, DOI : 10.1038/srep40262