Optimization of medium and process parameters for a constitutive α‐amylase production from a catabolite derepressed Bacillus subtilis 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 α‐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. Copyright © 2008 Society of Chemical Industry