A novel thermostable dextranase from a Thermoanaerobacter species cultured from the geothermal waters of the Great Artesian Basin of Australia.

A Gram-negative sporulating thermophilic anaerobe, designated AB11Ad, was isolated from the heated waters of the Great Artesian Basin of Australia. It grew on a variety of carbohydrates including glucose, starch, and dextran and produced a thermostable and thermoactive extracellular endo-dextranase. The enzyme was produced more actively under pH controlled continuous culture conditions than under batch conditions. Ammonium sulfate precipitated crude dextranase exhibited a temperature optimum of 70 degrees C and a pH optimum between 5 and 6. The half life was approximately 6.5 h at 75 degrees C and 2 h at 80 degrees C at pH 5.0 and in the absence of added dextran. 16S rRNA sequence analysis indicated that isolate AB11Ad was a member of the genus Thermoanaerobacter.