Biochemical Characterization of Dextranase from Arthrobacter oxydans and Its Cloning and Expression in Escherichia coli

Appreciably elevated levels of dextranase from Arthrobacter oxydans (AODex) isolated from sugar-cane farm soil was resulted from the culture on the Luria-Bertani (LB) medium containing 1%(w/v) soluble starch, glycerol, or dextran. The responsible gene (aodex) was cloned, its nucleotide sequence was determined, and expression of the encoded protein was achieved in Escherichia coli. An open reading frame was composed of 1,863 bp putatively encoding a 68.3 kDa protein. Recombinant A. oxydans dextranase (rAODex) was purified about 16 fold by nickel-nitrilotriacetic acid affinity column chromatography; K∧m value for dextran T2000 was 0.85 mg/mL (w/v). AODex treatment of stale sugar cane juice resulted in a yield of square and light-colored sugar crystals.