An indigenously isolated strain of Bacillus sphaericus was found to produce 1.21 IU/ml of tannase under unoptimized conditions. Optimizing the process one variable at a time resulted in the production of 7.6 IU/ml of tannase in 48 h in the presence of 1.5% tannic acid. A 9.26-fold increase in tannase production was achieved upon further optimization using response surface methodology (RSM), a statistical approach. This increase led to a production level of 11.2 IU/ml in medium containing 2.0% tannic acid, 2.5% galactose, 0.25% ammonium chloride, and 0.1% MgSO(4) pH 6.0 incubated at 37 degrees C and 100 rpm for 48 h with a 2.0% inoculum level. Scaling up tannase production in a 30-I bioreactor resulted in the production of 16.54 IU/ml after 36 h. Thus far, this tannase production is the highest reported in this bacterial strain. Partially purified tannase exhibited an optimum pH of 5.0 with activity in the pH range of 3 to 8; 50 degrees C was the optimal temperature for activity. Efficient conversion of tannic acid to purified gallic acid (90.80%) was achieved through crystallization. (C) 2011, The Society for Biotechnology, Japan. All rights reserved.