Cellulase-free Xylanase from Alkaliphilic Thermotolerant Bacillus halodurans Strain C-1 for Hydrolysis of Agricultural Residues and Kraft Pulps

Abstract

An alkaliphilic thermotolerant bacterium, Bacillus halodurans strain C-1, produces cellulase-free xylanasewhen grown in an alkaline xylan medium. The optimum pH of the enzyme activity was 6.0 and it retained 78%activity at pH 9.0. The enzyme was stable at pH 5.0 to 9.0 for 1 hour. The optimum temperature of the enzymewas 70 ^oC and it was stable at 40 to 60 ^oC for 30 minutes. The hydrolysis of agricultural residues and kraft pulpsby xylanase was studied at 50 ÌC and pH 9.0. The hydrolysis rate of xylan in corn hull was better than those ofsugarcane bagasse, rice straw, corn cop and rice bran. Alternatively, the hydrolysis rate of xylan in sugarcane pulpwas 2.7 and 7.5 folds higher than those of eucalyptus and pine pulps, respectively. However, rate of releasingchromophores from eucalyptus pulp was greater than sugarcane and pine pulps, respectively.

Keywords : Xylanase /Alkaliphilic Thermotolerant Bacillus halodurans Strain C-1 /Agricultural Residue / Kraft Pulp / Chromophore