Characterization of a recombinant cellobiose 2-epimerase from Caldicellulosiruptor saccharolyticus and its application in the production of mannose from glucose |
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Authors: | Chang-Su Park Jung-Eun Kim Jin-Geun Choi Deok-Kun Oh |
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Affiliation: | (1) Department of Bioscience and Biotechnology, Konkuk University, Seoul, 143-701, Republic of Korea; |
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Abstract: | A putative N-acyl-d-glucosamine 2-epimerase from Caldicellulosiruptor saccharolyticus was cloned and expressed in Escherichia coli. The recombinant enzyme was identified as a cellobiose 2-epimerase by the analysis of the activity for substrates, acid-hydrolyzed products, and amino acid sequence. The cellobiose 2-epimerase was purified with a specific activity of 35 nmol min–1 mg–1 for d-glucose with a 47-kDa monomer. The epimerization activity for d-glucose was maximal at pH 7.5 and 75°C. The half-lives of the enzyme at 60°C, 65°C, 70°C, 75°C, and 80°C were 142, 71, 35, 18, and 4.6 h, respectively. The enzyme catalyzed the epimerization reactions of the aldoses harboring hydroxyl groups oriented in the right-hand configuration at the C2 position and the left-hand configuration at the C3 position, such as d-glucose, d-xylose, l-altrose, l-idose, and l-arabinose, to their C2 epimers, such as d-mannose, d-lyxose, l-allose, l-gulose, and l-ribose, respectively. The enzyme catalyzed also the isomerization reactions. The enzyme exhibited the highest activity for mannose among monosaccharides. Thus, mannose at 75 g l–1 and fructose at 47.5 g l–1 were produced from 500 g l–1 glucose at pH 7.5 and 75°C over 3 h by the enzyme. |
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