PRODUCTION AND CHARACTERIZATION OF XYLANASE FROM LOCAL FUNGAL ISOLATES BY SUBMERGED FERMENTATIONVARSHA D. SAVANTH AND SEEMA J. PATEL
Xylanases showing better stability at alkaline pH and higher temperatures have potential applications in several industrial processes. The objective of this study is to determine the kinetic properties and thermal and alkaline stability of partially purified xylanase from Aspergillus niger isolates using birch wood xylan as carbon source. The fungal strains were isolated from soil of different places around Davangere, identified and preserved. Xylanase was extracted by submerged fermentation using these isolates on standard substrate. Further it was purified by ammonium sulfate (80 %) fractionation and dialysis. The molecular mass of the xylanase was ~ 22 kDa and the zymogram analysis indicated that this enzyme was an active xylanase. Highest xylanase activity of 1.222 units.mL-1 was obtained with the isolate 5. The optimum temperature was found to be 40°C and the pH optimum is in the range of 4-5. For xylan, the enzyme gave a highest Km value of 2.94 mg.mL-1 and Vmax value of 5.5 μmol.min-1.ml-1 for isolate 4, when the reaction was carried out at 40°C and pH 4.5. In the presence of metal ions such as Mg2+ and Cu2+, the activity of the enzyme increased, whereas, strong inhibition of the enzyme activity was observed in the presence of Hg+2and chelator EDTA. The hydrolysis study of birch wood xylan by TLC showed the formation of xylose as an end product.
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