A bacterial dextranase

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Abstract
Two bovine rumen strains and one human strain of Lactobacillus bifidus were shown to secrete an extracellular dextranase. The dextranase was isolated from cell-free culture fluids by precipitation with ammonium sulphate. Although the enzyme rapidly destroyed the opalescence of a dextran solution, reducing sugars were produced only after prolonged incubation. The products of the action of the enzyme on dextran were a mixture of isomalto-triose,-tetraose, -pentaose and higher oligosaccharides. Glucose and isomaltose were not produced. Isomaltose, isomalto-triose,-tetraose and -pentaose were not attacked by the enzyme. Isomaltohexaose was only slightly hydrolysed, whereas isomalto-heptaose and -octaose were hydrolysed readily. The dextranase had maximum activity in the range pH 5,4-6.5 and the temperature range 40-50 [degree]C.