BIOPROSPECTING XYLANASE ENZYMES FROM DIVERSE ECOLOGICAL HABITATS
International Research Journal of Natural and Applied Sciences
In order to exploit and improve the metabolic versatility of microorganisms , the classical area of research has been to optimize the production of extra cellular enzymes for efficient degradation of substrates and selection of advanced and more active enzymes for enhanced enzyme yield. Microbial xylanases are important group of industrial enzymes that are used for various commercial purposes. Wide variety of bacteria in the environment permits screening for efficient xylanase producing strains
... e producing strains to help overcome the current challenges. In an attempt to discover new xylanase producing strains, more than 600 actinomycete isolates representing varied ecological habitats were screened. By using birchwood xylan as substrate, diameter of zones of hydrolysis was measured and it ranged from 17-40 mm. Among the isolates tested, colonies 169, 126, and 202 along with the positive controls NRRL B-24314 (Streptomyces thermocoprophilus) and NRRL B-24916 (Streptomyces mexicanus) showing appreciable zones of clearance were selected for quantitative screening under the submerged state fermentation. Enzyme from respective colonies was partially purified by ammonium sulfate precipitation and dialysis. Enzyme activity ranged from 6.72-15.0 IU/ml (in crude) and 11.15-25 IU/ml (in partially purified). The highest enzyme producer, colony 169 was further purified to homogeneity by ion exchange chromatography. Activity estimated in purified fraction was 32.12 IU/ml. Colony 169 showed maximum xylanase activity 16.12IU/ml at pH range of 7.0-7.5, 16.22IU/ml activity at temperature range of 35 0 C-40 0 C and 16.44IU/ml substrate concentration of 1-1.5%. The fraction showed presence of two bands of approximately 50-55kDa and 60-65kDa as determined by SDS gel electrophoresis. Xylanase enzyme from colony 169 was analyzed with the help of proteomics MS/MS database. It was found that the enzyme type was endo-1, 4-beta-xylanase. Molecular analysis showed that the gene encodes a protein of 493 amino acid residues. Comparison of deduced amino acid sequence to other xylanases in the database indicated that the enzyme showed 63% similarity with Streptomyces lividans endo-1, 4-beta-xylanase and belongs to Glycoside hydrolase family 10. For construction of protein structure, homology modeling was done followed by structure verification. The efficiency of colony 169 in biodegradation of wastes was also studied.