| 摘要 |
PROBLEM TO BE SOLVED: To provide an enzyme for selectively producing only chitobiose by enzymatically hydrolyzing a chitosan and/or a chitosan oligomer, and further to provide a method for producing the chitobiose by using the enzyme. SOLUTION: This chitobiose-producing enzyme has the following physicochemical properties: (1) action and substrate specificity: acting on the chitosan and the chitosan oligomer, and hydrolyze them to each chitobiose unit; (2) optimum pH: about 4.5; (3) optimum temperature: about 50 deg.C; (4) thermal stability: stable to about 40 deg.C by the treatment at pH 6.0 for 30 min and to about 30 deg.C for 3 hrs; (5) pH stability: stable at pH 6.0-10.0 by the treatment at 30 deg.C for 3 hr and at pH 6.0-8.5 for 24 hrs; and (6) molecular weight: about 60,000 dalton (by gel filtration method).
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