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Screening and identification of a thermophilic and alkalophilic bacterium producing xylanase

SubajiniMahilrajan, Sandrasegarampillai Balakumar and Vasanthy Arasaratnam

This study focuses on screening and identification of bacteria, which can produce alkaline xylanase at alkaline pH and high temperature. Bacterial isolates from corncob decaying soil, capable of hydrolyzing xylan were screened. Selected and purified 108 bacterial colonies grown on xylan- nutrient agar slants were activated and transferred into the fermentation medium. Six highest xylanase producing isolates were selected for further studies. Isolates CS1[132.0(±0.09)], CS27[121.3(±0.11)]& CS88 [124.8(±0.44) UmL-1] showed highest xylanase production at pH 8.5 while isolates CS52[124.4(±0.01) UmL-1], CS93[113.0(±0.48) UmL-1] and CS104[110.1(±0.54) UmL-1] showed at pH 8.0 and 45oC. Therefore isolates CS1, CS27 & CS88 were selected and the xylanase produced by them were screened for the kinetic properties. The crude enzymes of the isolates CS1, CS27 & CS88 showed zero order kinetics up to 4 min. The optimum temperature for the activity of the xylanase from isolates CS1 and CS27 was 55oC, while that of isolate CS88 was 60oC. The optimum pH value for the xylanase from isolate CS1 and CS88 was 8.4 and that of isolate CS27 was 8.0. Based on the kinetic properties of xylanase, isolates CS1 and CS88 were selected and characterized and found to be belonging to genus Bacillus. As Bacillus CS1 produced highest xylanase activities, 16S rDNA was analyzed and identified as Bacillus pumilus and selected for further studies to produce xylanase at 45oC and pH 8.5.