A New Method of Preparation of Isomaltose from Acid-treated Dextranby Isomalto-dextranase
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概要
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Isomalto-dextranase [EC 3.2.1.94] from Arthrobacter globiformis catalyzes the hydrolysis of α-1, 6 linkages of dextran and isomalto-oligosaccharides to liberate isomaltose from the non-reducing ends of those sugars. A new method for the preparation of isomaltose was developed by using the isomaltodextranase and an acid-treated dextran. When dextran T2000 was used as a substrate, the maximal degree of hydrolysis by the isomalto-dextranase was less than 40%. For this reason, the enzyme reaction was thought to be hindered at the branch points (α-1, 2, α-1, 3 and α-1, 4-glucosidic linkages) of dextran. The branch points of dextran were presumed to be selectively hydrolyzed by an appropriate mild acid pretreatment, because theα-1, 6-glucosidic linkage constructing main chain of dextran is less acid-labile than other α-1, 2, α-1, 3, α-1, 4-glucosidic linkages. Therefore, dextran was incubated at 95°C for 4 hr in 0.2 N hydrochloric acid. When the dextran treated with 0.2 N hydrochloric acid was acted on by the enzyme, the maximal degree of hydrolysis went up to over 90%. Consequently, the branch points were considered to be hydrolyzed selectively. In order to enable the continuous preparation of isomaltose, the acid-treated dextran and isomalto-dextranase were confined in the DIAFLOTM cell with the ultrafiltration membrane. The products were taken out through the membrane of the apparatus. By this system, 6 g of isomaltose was obtained from 200 ml of 5% acid-treated dextran.
- 日本応用糖質科学会の論文
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