Abstract
A GH49 dextranase gene DexKQ was cloned from marine bacteria Arthrobacter oxydans KQ11. It was recombinantly expressed using an Escherichia coli system. Recombinant DexKQ dextranase of 66 kDa exhibited the highest catalytic activity at pH 9.0 and 55 °C. kcat/Km of recombinant DexKQ at the optimum condition reached 3.03 s−1 μM−1, which was six times that of commercial dextranase (0.5 s−1 μM−1). DexKQ possessed a Km value of 67.99 µM against dextran T70 substrate with 70 kDa molecular weight. Thin-layer chromatography (TLC) analysis showed that main hydrolysis end products were isomalto-oligosaccharide (IMO) including isomaltotetraose, isomaltopantose, and isomaltohexaose. When compared with glucose, IMO could significantly improve growth of Bifidobacterium longum and Lactobacillus rhamnosus and inhibit growth of Escherichia coli and Staphylococcus aureus. This is the first report of dextranase from marine bacteria concerning recombinant expression and application in isomalto-oligosaccharide preparation.
Highlights
Dextranase (EC 3.2.1.11) catalyzes the hydrolysis of dextran (α-1,6-glucosidic glucan). It is classified as endo- and exo-dextranase based on the mode of action
Arthrobacter oxydans KQ 11 isolated from China coastal sediment could produce a highly active dextranase, which has been studied in our previous report [4]
KQ11 was purified from its culture supernatant and characterized
Summary
Dextranase (EC 3.2.1.11) catalyzes the hydrolysis of dextran (α-1,6-glucosidic glucan). It is classified as endo- and exo-dextranase based on the mode of action. Many microorganisms, including mold, yeast, and bacteria, can produce dextranase [1]. Many new polysaccharide hydrolases, including chitinase, chitosanase, alginate lyase, agarose, and carrageenase, have been found in marine microorganisms [3], but there are few reports about marine bacteria producing dextranase. Arthrobacter oxydans KQ 11 isolated from China coastal sediment could produce a highly active dextranase, which has been studied in our previous report [4]. Due to the low enzyme yield in native Arthrobacter oxydans strains, the application of this dextranase was limited. Some characterization and applications of recombinant dextranase were investigated in this study
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