BACKGROUND: In Bacillus subtilis KCC103 alpha-amylase is hyper-produced and not catabolite repressed by glucose. Various sugars, raw starches and nitrogen sources were tested for their repression effect on alpha-amylase synthesis. Enhancement of alpha-amylase production by supplementing micronutrients and surfactants was studied. Using optimized medium, process parameters were optimized for improved alpha-amylase production. RESULTS: alpha-Amylase was produced from KCC103 utilizing simple sugars indicating the absence of catabolite repression. Raw potato and yeast extract were best carbon and nitrogen sources for alpha-amylase production. alpha-Amylase synthesis was enhanced by micronutrients cysteine, thiamine, Mg2+ and SDS. Maximum alpha-amylase (394 IU mL(-1)) was produced in the optimized medium consisting of (in g L-1) raw potato (30.0), yeast extract (20.0), cysteine (0.3), thiamine (0.2), SDS (0.2) and MgSO4 (0.5 mmol L-1) at 36-48 h under optimal conditions (pH 7.0, 37 degrees C, 200 rpm). The alpha-amylase production was further enhanced to 537.7 IU mL(-1) with shorter time (15-18h) in a bioreactor with optimized agitation rate of 700 rpm at 30% dissolved oxygen. CONCLUSION: Since there was no carbon catabolite repression of alpha-amylase synthesis, sugar mixture from various agro-residues hydrolysates could be utilized for alpha-amylase production. The study showed the feasibility of utilization of raw potato for alpha-amylase production from the KCC103, which would lead to a significant reduction in process cost. (c) 2008 Society of Chemical Industry.