Hyper Production and Eco-Friendly Bleaching of Kraft Pulp by Xylanase From Bacillus pumilus SV-205 Using Agro Waste Material

Abstract

Hyper production of an extra cellular, alkali stable, cellulase free and thermostable xylanase have been produced from Bacillus pumilus SV-205 using wheat bran as a substrate under solid state fermentation. Enzyme production under optimized conditions enhanced the production level from 4510 to 65,130 ± 1000 IU/g dry substrate, which was 14.4 fold as compared to production under un-optimized conditions. The application of crude xylanase was investigated in pulp bio bleaching. The bio-bleaching of kraft pulp with xylanase was the most effective at an enzyme dose of 12.5 IU/g oven dried pulp, pH 10.0 and 120 min incubation at 60 °C. Under the optimized conditions, xylanase pre-treatment reduced Kappa number by 0.8 points and increased brightness by 1.08 points as compared with the control. The pre-treatment of pulp with xylanase resulted in 19.01% reduction in chlorine consumption by maintaining the same brightness as in control. These results clearly demonstrated that the B. pumilus SV-85S xylanase was effective as a pulp bio-bleaching agent. The decrease in chlorine consumption by pre-treatment of pulp with xylanase apparently made the bio-bleaching process not only economical but also eco-friendly. The xylanase from B. pumilus SV-205 exhibit remarkable properties which are suitable for application in paper pulp bleaching and an elevated production of xylanase by B. pumilus SV-205 under solid state fermentation over wheat bran, a cheap and easily available agro-residue would apparently reduce the enzyme cost substantially.