Optimizing mechanical pretreatment of cotton textile waste to enhance enzymatic hydrolysis

• A minimum energy threshold is necessary during wet milling. • Significant effects of solids load and gap width on enzymatic degradation. • A reduction in the crystallinity index correlates with increased glucose yield. • The cellulase blends demonstrate tolerance to impurities in textile waste. Enzymatic recycling processes of cotton from waste materials have gained increasing interest in recent years. Therefore, the aim of this study was to optimize the application of mechanical shear forces to end-of-life cotton-based textile suspensions, followed by an enzymatic hydrolysis to glucose. Mechanical pretreatment in a cutting mill followed by a wet-rotor-milling process was investigated by varying solids load and mill parameter settings. The results indicated that both a smaller gap width and higher solids load during mechanical pretreatment resulted in enhanced enzymatic hydrolysis. Additionally, it was found that a minimum amount of energy input while milling was necessary to enable a higher glucose yield. The relationship between energy input, enzymatic hydrolysis, and crystallinity facilitates the assessment of the effect of energy input within the milling process. Furthermore, a decrease in enzyme activity was observed with increasing solids load during enzymatic hydrolysis. Overall, the findings of this research suggest that wet milling presents a promising technology to improve the enzymatic hydrolysis of end-of-life cotton textiles.