Optimization of medium and process parameters for a constitutive α-amylase production from a catabolite derepressed Bacillus subtllis KCC103

Background: In Bacillus subtilis KCC103 α-amylase is hyper-produced and not catabolite repressed by glucose. Various sugars, raw starches and nitrogen sources were tested for their repression effect on α-amylase synthesis. Enhancement of α-amylase production by supplementing micronutrients and surfactants was studied. Using optimized medium, process parameters were optimized for improved α-amylase production. Results: α-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 a-amylase production. α-Amylase synthesis was enhanced by micronutrients cysteine, thiamine, Mg2+ and SDS. Maximum α-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°C, 200 rpm). The α-amylase production was further enhanced to 537.7 IU mL-1 with shorter time (15-18 h) in a bioreactor with optimized agitation rate of 700 rpm at 30% dissolved oxygen. Conclusion: Since there was no carbon catabolite repression of α-amylase synthesis, sugar mixture from various agro-residues hydrolysates could be utilized for α-amylase production. The study showed the feasibility of utilization of raw potato for α-amylase production from the KCC103, which would lead to a significant reduction in process cost. © 2008 Society of Chemical Industry.