Biochemical evaluation of xylanases from various filamentous fungi and their application for the deinking of ozone treated newspaper pulp

•Aspergillus oryzae yielded very high amount of xylanase (34,442IU/g) at tray level (24×19×5cm3).•Xylanase from A. oryzae has high affinity with beechwood xylan with least Km value (3.33mg/ml).•Ozone treatment resulted in high crystallinity index (72.1%) and more fibrillar surface.•Xylanase treatment of newspaper pulp resulted in improved brightness (57.9% ISO) and ERIC value (211ppm). Filamentous fungi, Aspergillus oryzae MDU-4 was biochemically selected among different species of Aspergillus and Trichoderma, for xylanase production. The enzyme activity and specific activity of partially purified xylanase from A. oryzae MDU-4 was 7452IU/ml and 13,549IU/g, respectively. Temperature and pH optima for xylanase were found to be 60°C and 6.0, respectively. The reaction kinetics of xylanase was found to be Km (3.33mg/ml) and Vmax (18,182μmol/mg). The implementation of ozone treatment in the deinking of newspaper pulp resulted in high crystallinity index (72.1%) and more fibrillar surface. Furthermore, the xylanase treated pulp showed significant improvement in optical properties such as brightness (57.9% ISO) and effective residual ink concentration (211ppm). Scanning electron microscopy analysis suggests perforations in xylanase treated pulp samples. Here we report biochemical evaluation of xylanases and a combination of ozone treatment followed by catalytically efficient fungal xylanase selected for the cost competitive deinking of newspaper pulp.