Production of α-amylase by Aspergillus oryzae As 3951 in solid state fermentation using spent brewing grains as substrate

BACKGROUND: The optimisation of nutrient levels for the production of α-amylase by Aspergillus oryzae As 3951 in solid state fermentation (SSF) with spent brewing grains (SBG), an inexpensive substrate and solid support, was carried out using response surface methodology (RSM) based on Plackett–Burman design (PBD) and Box–Behnken design (BBD). RESULTS: In the first optimisation step a PBD was used to evaluate the influences of related factors. Corn steep liquor, CaCl2 and MgSO4 were found to be the most compatible supplements to the substrate of SBG and influenced α-amylase activity positively. In the second step the concentrations of these three nutrients were optimised using a BBD. The final concentrations (g/g dry substrate basis) in the medium optimised with RSM were 1.8% corn steep liquor, 0.22% CaCl2 and 0.2% MgSO4 · 7H2O using SBG as the solid substrate. The average α-amylase activity reached 6186 U g−1 dry substrate under the optimised conditions at 30 °C after 96 h. Under the optimised conditions of SSF an approximately 17.5% increase in enzyme yield was observed. CONCLUSION: SBG was found to be a good substrate for the production of α-amylase by A. oryzae As 3951 under SSF. Copyright © 2007 Society of Chemical Industry