Kinetic parameters of Aspergillus awamori in submerged cultivations on whole wheat flour under oxygen limiting conditions

Abstract The kinetic parameters of fungi like Aspergillus awamori may vary significantly according to culture conditions, such as oxygen and fermentation media. The knowledge of maximum growth rate and growth yields is necessary for process optimisation, modelling and scale-up. The measurement of such parameters is hindered on fermentations where complex, heterogeneous medium is utilised. This study focuses on the determination of kinetic parameters such as maximum specific growth rate (0.28 h−1) and growth yields on substrate (0.31 g g−1) and oxygen (0.22 g g−1) for A. awamori growing under oxygen limiting conditions on whole wheat flour in submerged culture. The low growth yields indicated the effect of oxygen depletion on fungal kinetic parameters. A specific glucoamylase production of 72 U g−1 h−1 has been observed. The unstructured mathematical model used to simulate fermentation variables takes into account fungal growth, dissolved oxygen, glucose consumption, starch hydrolysis, glucoamylase activity, volumetric oxygen transfer coefficient and apparent viscosity. The fungal growth has been estimated using on-line measurements of CO2 evolution during fermentation.

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