Optimization of agro-residual medium for α-amylase production from a hyper-producing Bacillus subtilis KCC103 in submerged fermentation

BACKGROUND: Although submerged fermentation (SmF) is the conventional method in industry, use of low-cost agro-residues for alpha-amylase production in SmF has not been well established. Here we optimized agro-residue-based medium and culture conditions for alpha-amylase production in SmF using a hyper-producing Bacillus subtilis KCC103. RESULTS: B. subtilis KCC103 produced alpha-amylase in SmF by utilizing agro-residues. Wheat bran l and sunflower oil cake (SFOC) were selected as the best substrates using shake flasks. Medium containing WB (carbohydrate rich) and SFOC (rich in protein and free amino acids) at 1:1 (w/w) ratio produced high levels (90 IU mL(-1)) of alpha-amylase at 30-36 h in a shake flask. The alpha-amylase yield was 14-fold enhanced (1258 IU mL(-1)) by optimizing process parameters and medium composition following response surface methodology in a bioreactor. The optimal conditions were: WB 1.27%, SFOC 1.42%, pH 7, 37 degrees C and 10-12 h. Both in shake flask and bioreactor alpha-amylase synthesis was not repressed by the release of simple sugars into the medium. CONCLUSION: KCC103 with catabolite derepression and hyperproducing ability is useful for economic alpha-amylase production using low-cost agro-residual substrates in conventional SmF. Since the production time (10-12 h) is much shorter than other strains this would improve productivity and further reduce the cost of alpha-amylase production. (c) 2008 Society of Chemical Industry