Enzymes in Circular Cellulose Fibre Biorefinery

Restrictive legislation pressure on industry promotes developing technologies that minimizing waste quantity, energy consumption and intensifying circular production process. This requires adaptions in manufacturing processes which have to be concerted with waste recycling steps and energy consumption profiles. Enzymes as environmentally friendly biocatalysts can play a major role to achieve a circular production cycle in the cellulose fibre area. Here we will discuss various examples of enzyme application in processing and recycling of cellulose fibres. Related to paper production, investigations demonstrated a considerably reduced refining energy demand of approx. 29% upon addition of cellulase enzyme cocktails1. For successful implementation of this process, however, a deeper mechanistic understanding of basic enzymatic function on fibres is required especially for predicting the effect of enzymes. For example, such investigations involve analytical and imaging techniques (GPC, HPLC_MSTOF, SEM, AFM) in combination with test trials producing and characterizing hand sheets. In addition to cellulose fibre processing, their recovery from waste streams is gaining increasing importance in a circular economy. Enzymes can be used to hydrolyse cellulose fibres (fragments) contained in deinking sludge allowing recovery of valuable glucose. Investigations indicate, that the recovered glucose in turn can then serve as carbon source for on-site microbial production of those enzymes needed in deinking or in other pulp & paper processing steps. Another successful example is the recycling of rayon fibres. Experiments using rayon fibres from waste streams clearly indicated successful enzymatic hydrolysis and biotechnological utilization of the formed glucose for the formation of various bioproducts ranging from ethanol to chemical building blocks (e.g. lactic acid). Furthermore, it was possible to reuse high value pigments after enzymatic hydrolysis of rayon fibres3. All these applications within a circular biorefinery rely on the use of cellulase enzymes, either for controlled cellulose fibre modification or for complete hydrolysis. 1.Singh, R. Cellulase-assisted refining optimization for saving electrical energy demand and pulp quality evaluation. 74, 471 -475 (2015). 2.Dimarogona, M., Topakas, E. & Christakopoulos, P. Cellulose Degradation By Oxidative Enzymes. Comput. Struct. Biotechnol. J. 2, 1 -8 (2012). 3.Vecchiato, S. et al. Enzymatic Recycling of High-Value Phosphor Flame-Retardant Pigment and Glucose from Rayon Fibers. ACS Sustain. Chem. Eng. 6, 2386 -2394 (2018).