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

摘要

BACKGROUND: In Bacillus subtilis KCC103 -amylase is hyper-produced and not catabolite repressed by glucose. Various sugars, raw starches and nitrogen sources were tested for their repression effect on -amylase synthesis. Enhancement of -amylase production by supplementing micronutrients and surfactants was studied. Using optimized medium, process parameters were optimized for improved -amylase production. RESULTS: -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 -amylase production. -Amylase synthesis was enhanced by micronutrients cysteine, thiamine, Mg2+ and SDS. Maximum -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 -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 -amylase synthesis, sugar mixture from various agro-residues hydrolysates could be utilized for -amylase production. The study showed the feasibility of utilization of raw potato for -amylase production from the KCC103, which would lead to a significant reduction in process cost.