Valorization of Agro-industrial Residue-Rice Straw for Manufacturing Better Quality Paper Using Cleaner, Ultrafiltered Xylano-Pectinolytic Enzymatic Pulping Strategy

In this study, eco-friendly pulping of rice straw for manufacturing better quality paper is presented, using ultrafiltered xylanase and pectinase enzymes. The optimum conditions of ultrafiltered biopulping were, xylanase:pectinase dose 300:105 IU/g, treatment time 180 min, pulping consistency 10%, temperature 55 °C and pH 8.5. The ultrafiltered biopulping resulted in higher residual alkali content (29.17%). The kappa number, rejects, total solids reduced by 14.71%, 15.85%, 7.89%, respectively. In order to attain the approximately similar optical properties, as obtained with conventional pulping, ultrafiltered biopulping of rice straw resulted in 12% reduction in toxic pulping chemical and also improved the strength of handsheets with breaking length (16.08%), burst index (27.53%), tear index (4.36%), double fold (40%), gurley porosity (20.62%) and viscosity (11.30%). The ultrafiltered biopulping also reduced the consumption of bleaching chemical dose. The various strength related properties of biopulped (with 12% reduced alkali dose) and bleached rice straw pulp samples were significantly higher than 100% chemically treated pulp samples with breaking length (17.13%), burst index (21.16%), tear index (5.68%), double fold (39.58%), gurley porosity (25.81%) and viscosity (28.57%). This is the first report demonstrating the reduction of chemical dose in pulping and as well as in bleaching of rice straw along with production of better quality paper. Graphical Abstract