Optimization of Extraceliular Celiulase—free Xyianase Production by Aikaliphilic Bacillus firmus K—1

Abstract

When an alkaliphilic bacterium Bacillus firmus K—1 was grown in alkaline xylan medium,pH 10.5, it produced extracellular cellulase—free xylanase that has a potential to use in pulp prebleaching process. Due to the high price of xylan, Optimization of media for the extracellular cellulase—free xylanase production by the Bacillus firmus K-1 using various agricultural wastes as  carbon sources instead of xylan and various nitrogen sources in shaking flask was studied. It was found that 1.0% corn hull was the best carbon source for production of the xylanase when compared with the other agricultural wastes such as rice straw, corn cob, sugarcane bagasse and rice bran. For the nitrogen source, 0.4% urea was found to be the best when compared with ammonium nitrate, ammonium sulfate, sodium nitrate and potassium nitrate. The optimized alkaline medium gave the specific xylanase activity of 3.0 U/mg protein, resulting 62% increase of the activity when compared to that obtained in the alkaline mineral salt medium with 0.5% xylan and 0.2% sodium nitrate. The mineral salts in the form of CaCl₂ , FeSO₄ and MgSO₄ had no effect on xylanase production whereas CoSO₄, ZnCI₂, and CdSO₄ inhibited the production of xylanase.

Keywords : Extracellular Cellulase—free Xylanase / Alkaliphilic Bacillus firmus K—1 /Optimization of Medium / Pulp Prebleaching / Corn Hull