Textile recycling – Characterization of endoglucanase activities in commercial cellulase formulations for use in cotton/polyester separation

The global production of textile fibers has been increasing for years reaching 113 million tons in 2021 with 54 % being polyester and 22 % cotton (Opperskalski et al., 2022). In Austria 212 800 tons of textile waste ended up in residual waste in 2018 (Bernhardt, et al., 2022). The aim of this work is to separate cotton and polyester sustainably using cellulase formulations preserving the polymer structure of cellulose and polyester. For an efficient process, an optimal combination of these enzymes is required. Different enzyme formulations were tested and characterized regarding their protein concentration and kinetic parameters during cellulose degradation. Cotton is primarily composed of cellulose (Haigler et al., 2012), which can be degraded by an interacting group of enzymes called cellulases: endoglucanases cleave the cellulose chains randomly, cellobiohydrolases degrade cellulose from the ends and their end product cellobiose is hydrolysed by cellobiases to glucose (Cavaco-Paulo, 1998). Different substrates were used to evaluate the activity of the cellulases. Carboxy methyl cellulose is used to determine the endo-activity and filterpaper the total cellulase activity (Ghose, 1987). The enzyme activities were calculated by measuring the resulting reducing sugars by the neocuproine method (Cavaco-Paulo et al., 1996). Reducing and non-reducing SDS-PAGE was used to analyse the composition and possible polymer structures of enzymes in formulations. Further a semi-preparative size exclusion chromatography was carried out to in order to obtain protein fractions of ideally different enzymatic activities and subsequently create optimal conditions for the separation and recycling process. Our findings will contribute to the effective and eco-friendly recycling of textiles.