An eco-friendly and efficient bio-degumming approach for sisial fibers preparation with closed-loop recycling of degumming wastewater

Degumming is an indispensable processing stage for plant fiber preparation, whereas the resulting degumming wastewater poses significant environmental challenges due to its high chemical oxygen demand (COD) concentration. This study explored the effects of three different degumming methods (C RSF : Chemical degumming of raw sisal fibers; B FSL : Bioaugmentation degumming of fresh sisal leaves; B RSF : Bioaugmentation degumming of raw sisal fibers) on sisal fiber preparation and COD footprint in degumming wastewater. The results showed that B RSF method not only achieved the highest gum removal efficiency and fiber yield, but also endowed the prepared sisal fibers with exceptional cellulose content, fiber crystallinity, thermal stability, and superior physical and mechanical properties. Notably, B RSF method displayed superior eco-friendly performance with a minimum COD concentration at 718.83 mg/L, whereas C RSF method yielded COD up to 6202.31 mg/L. Owing to containing bioavailable compositions such as sugar and nitrogen, the wastewater generated by B RSF was reused as fermentation substrate for Pichia pastoris Y05 production. The developed recycling system not only obtained substantial microbial biomass, but also achieved the COD removal efficiency of degumming wastewater up to near 90 %. In summary, this study successfully established an eco-friendly and efficient bio-degumming approach for sisial fibers preparation with closed-loop wastewater recycling. • The established B RSF strategy considerably shortened the microbial degumming duration. • B RSF strategy significantly improved the physical and mechanical properties of sisal fibers. • B RSF strategy minimized fiber damage and chemical pollution by traditional chemical degumming. • Degumming wastewater of B RSF realized recycling and bioremediation.