Cleaner bio-pulping approach for the production of better strength rice straw paper

Abstract

The aim of this study was to explore the potential of crude xylano-pectinolytic enzymes in bio-pulping of rice straw, in order to reduce environmental pollution. In this study, the effect of integration of bio-pulping strategy before chemical pulping of rice straw has been investigated. The bio-pulping efficiency was found to be maximum at xylanase:pectinase dose of 400:120 IU/g rice straw, temperature 55 °C, treatment time 3 h, Tween 80 (1%), pH 8.5 and pulping consistency 1:10 (g/mL). Bio-pulping enhanced the permeability of pulping chemicals, generated pulp with higher yield, brightness, along with higher residual active alkali content of black liquor in comparison to the pulp obtained after chemical pulping. Bio-pulping also resulted in 10% reduction of alkali dose and improved paper quality, with increase in breaking length (13.9%), burst index (27.0%), double fold (39.3%), gurley porosity (18.75%) and viscosity (8.77%) of unbleached bio-pulp. Bio-pulping also improved the bleachability by removing the D2 step of bleaching and produced pulp with higher physical strength properties, breaking length (15.92%), burst index (20.47%), tear index (3.87%), double fold (36.0%), gurley porosity (25.0%) and viscosity (28.36%). Hence, this environmentally sustainable bio-pulping approach can decrease the chemical load and ultimately pollution, along with enhance the yield and quality of paper. This is the first report demonstrating cleaner pulping of rice straw using crude xylano-pectinolytic enzymes, produced by a bacterial isolate.