Production of Alkali-Tolerant Xylanases from Bacillus pumilus and application in pre-bleaching of kraft pulps

RESUMO

This work investigated the production of alkali-tolerant xylanases produced by Bacillus pumilus. Xylanases active at alkaline conditions and high temperatures have great potential for industrial application, such as the bleaching process in pulp and paper industry, without need for cooling or changes in pH and whith the advantage in lowering the release of polluting organic chlorine compouds. Optimal condition of cellulase-free xylanase in submerged fermentation were developed. The highest xylanase production in culture flasks, 129 U/mL at pH 9 and 55 C, was obtained in 20 hours of fermentation, with 3(per cent) xylan, 0,6(per cent) peptone, 0,15(per cent) ammonium sulphate at pH 9,5, achieving a productivity of 6.5 UmL -1h-1. The productivity raised to 17.3 UmL -1h-1 when the xylanase was produced in 2.0 L bioreator. Xylanase form crude fermented broth was applied for pre bleaching of harwood kraft pulp. A decrease of 2,5 units in kappa number 26(per cent) delignification) was observed, indicating the potential for the alkaline xylanase from B. pumilus.