An increased production and consumption of textiles with a simultaneous shortening of their lifespan has led to a serious waste problem. While fiber recycling of unblended natural and synthetic fiber is already possible solutions for mixed-fiber textiles are still required. One potential approach is to degrade the minor component of the mixed-fiber textile enzymatically and further reprocess the major component to new fibers. Cellulases have been successfully applied for cellulose degradation within cellulose/polyester mixed-fiber textiles but further optimisation is needed to obtain an economic viable process. Characteristically, cellulose records a high crystallinity, which is generally known to complicate its digestibility. To overcome this problem, a pretreatment e.g. with acids or alkalis, to generate amorphous cellulose and increase its conversion rate is mandatory. In this study alkaline pretreatment of mixed-fiber textiles has successfully been optimised using a central composite design. A special focus was thereby set to additives as urea or ultrasonic pulses.