Potential recycling of cellulase formulations for cotton/polyester separation: identification of enzymatic activity trends during reuse

Textile waste largely consists of blended fabrics, of which cotton/polyester blends represent one of the most important material streams. The separation of these two polymers is essential for their recycling. Biotechnological tools offer a promising approach by using specific enzymes, cellulases. Hereby the cotton content, mainly consisting of cellulose, is degraded through enzymatic hydrolysis to glucose, while the polyester fraction remains largely intact. High process costs resulting from low hydrolysis rates and relatively large quantities of cellulases used, are currently still an obstacle to upscaling and thus industrial application.
In this contribution, we present results of the investigation of the recyclability of commercially available cellulase formulations for the treatment of cotton/polyester blended textile waste by measuring the enzyme activity and monitoring of degradation products. Specifically, a particular enzyme formulation is used for several consecutive cotton degradation cycles on cotton/polyester substrate and its recyclability is evaluated by parameters like protein concentration (Bradford and SDS-PAGE) and additionally, their activity is observed via filter paper assay. The cotton degradation products are quantified using HPLC and the reducing sugar content (neocuproine method) to continuously monitor the glucose amount in the solution. The quantitative change of the substrate after each cycle is determined by the total fabric weight loss and related cellulose hydrolysis. The initial solution is reused for all further sequential degradation cycles, while, after removal of the substrate from the previous cycle, new substrate of constant quality and quantity is added. With this experimental setup, trends in hydrolysis rate and cotton degradation efficiency become visible and the feasibility of reusing cellulase formulations is evaluated, which may help to enable industrial application of this enzyme technology by minimizing process costs and thereby achieving improved recyclability of cotton/polyester blended textiles.