Optimum production of extracellular, thermostable amylolytic enzymes (alpha and beta-amylase) by a newly isolated bacterium, Bacillus stearother-mophilus, was investigated in a batch bioreactor. Starch and lactose at 1.0% and 3.0% (w/v) respectively were found to be optimum for maximum enzyme production. Optimization of cultural conditions (pH 7.0 and temperature 45 degrees C) resulted in high bacterial specific growth rate (0.64 h(-1)), yielding 2.20 gL(-1) biomass, 11.43 UmL(-1) alpha-amylase and 10.04 UmL(-1) of beta-amylase. Hydrolysis of native starches from wheat, cassava, corn and potato at 60 degrees C using the crude enzyme showed 60-80% saccharification with potato starch showing the least and wheat starch showing the greatest hydrolysis. The K-m and V-max. values of the crude alpha-amylase for starch were 4.78 mg starch/mL and 6.67 mg/mL.min respectively.