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

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 7452 IU/ml and 13,549 IU/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 (3.33 mg/ml) and Vmax (18,182 μmol/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 (211 ppm). 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.