Screening of actinomycetes for dextranase production was carried
out using blue-dextran as described by Barrett and Curtiss (1986). The isolate giving highest ratio of zone of clearance to colony diameter was chosen for further studies. Dextranase production was carried out in the medium with 15 g dextran, 3 g NaCl,
0.2 g MgSO4, 1 g NH4H2PO4, 1 g of K2HPO4 per liter (Hattori et al.,
1981). The production of dextranase was monitored for 6 days with incubation at 37 C and 150 rpm. The enzyme activity was determined every 24 h by monitoring the release of reducing sugars due to the action of dextranase on dextran. The cell free supernatant was incubated with equal amount of 2% dextran in 50 mM
phosphate buffer (pH 7.0) and incubated at 37 C. Dextranase activity was measured by method of Miller (1959) using glucose as a standard. One unit of dextranase activity is defined as the amount of enzyme producing 1 lmol of reducing sugar per minute under the above-mentioned conditions. Protein concentrations were determined by the method of Lowry et al. (1951) using bovine serum albumin as a standard.