Dual application of agricultural residues for xylanase production and dye removal through solid state fermentation

The present study is a novel attempt to utilize agricultural residues for addressing the dual challenge faced by pulp and paper industries to control pollution caused due to pulp bleaching and release of colored waste water. Fungal isolate, Aspergillus lentulus, was utilized for the production of xylanase through solid state fermentation utilizing various low-cost agro-residues as substrate. Maximum xylanase production was obtained on the 4th day of incubation using wheat bran as the substrate (158.4 U/g) followed by corn cob (153.0 U/g), sugarcane bagasse (129.9 U/g) and wheat straw (49.4 U/g). These activities were accompanied by very low cellulase activities. The enzyme exhibited good stability at high pH and temperature (>75% activity retained at pH 9 and 70 °C). Later, the left over spent fermented slurry was utilized to remove anionic (>85.0% removal) and cationic (>96.0% removal) dyes. Results indicate cellulase-free; pH and thermo stable nature of the xylanase enzyme which is required during bio-bleaching process. Moreover, successful utilization of spent residues from fermentation in dye removal process signify that the proposed technology can be utilized to meet the requirements of pulp and bleaching industries through an effective and sustainable approach.