Towards a resource friendly circular cotton processing: From carbohydrate rich wastewaters to hydrogen peroxide using carbohydrate oxidases

One of the main concerns in the textile cotton industry is the substantial amount of contaminated effluent generated from various stages, including desizing and pre-wash. The wastewater, rich in carbohydrates from starch hydrolysis, presents a promising feedstock for hydrogen peroxide (H2O2) production, a crucial component in cotton fabric bleaching. this study, comprehensively characterized various cotton processing wastewater, evaluating their total sugar content and carbohydrate profile. Based on the results, wastewater from the pre-washer emerged as the most suitable for enzymatic H2O2 production. Given the variability in carbohydrate profile of wastewater, two strategies based on the carbohydrate oxidase promiscuity were developed: N-ace tylglucosamine oxidase (NagOx), specific for glucose, and Cellobiose oxidase (COX), displaying a high carbohydrate promiscuity. A pretreatment with glucoamylases was employed to increase glucose levels for NagOX, while COX was directly applied towards untreated wastewater. pH control was assessed for both systems.

Results indicated NagOX’s performance was enhanced by pH control, unlike COX. The robustness and flexibility of both proposed strategies were validated using diverse batches industrial wastewaters samples, confirming the efficacy of the proposed enzymatic-based hydrogen peroxide production processes. Biobleaching tests were conducted, revealing an impact of wastewater color on the bleaching process. However, the use of a hydrogen peroxide activator (TAED) emerged as a promising approach to implement the proposed strategies.