Compatibility testing and enhancing the pulp bleaching process by hydrolases of the newly isolated thermophilic Isoptericola variabilis strain UD-6

Abstract

In the present study, Isoptericola variabilis strain UD-6 isolated from alkaline hot spring of Unapdev, Maharashtra, India was assessed for its biobleaching activity by hydrolytic enzymes on rice straw pulp. Results of primary and secondary screening manifested that it was a multi-enzyme producer, competent to produce amylase, cellulase, mannanase, pectinase, and xylanase at 9.73, 4.11, 6.26, 8.42, and 6.61 IU ml−1 in fermentation conditions, respectively. Maximum activity of all enzymes was gained at thermal temperature (50–55 °C), alkaline condition (pH 8–9), under 5 mM KCl and 5 mM NaCl salt concentration. In compatibility testing, activities of all enzymes were spectacularly reduced when they utilized with chemicals of pulp bleaching. Results of rice straw pulp bleaching was effectual when pulp was initially bleached with mannanase, pectinase, and xylanase enzymes (Es) for 90 min and then with diluted chemicals (DC) for further 90 min instead of their separate use. Treatment of rice straw pulp with Es + DC, enhanced the release of reducing sugars, hydrophobic compounds, and phenolic compounds, whereas Kappa number was reduced. Overall, the results of the present study indicated that pre-bleaching of pulp with hydrolytic enzymes obtained from I. variabilis strain UD-6 helps to minimize chemicals used in the bleaching process and make it more sustainable for pulp and paper industries as well as for the environment.