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 Aus tralia. It grew on a variety of carbohydrates including glucose, starc h, and dextran and produced a thermostable and thermoactive extracellu lar endo-dextranase. The enzyme was produced more actively under pH co ntrolled continuous culture conditions than under batch conditions. Am monium sulfate precipitated crude dextranase exhibited a temperature o ptimum of 70 degrees C and a pH optimum between 5 and 6. The half life was similar to 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 indi cated that isolate AB11Ad was a member of the genus Thermoanaerobacter .