Kinetic Analysis of Aspergillus oryzae Cultivations on Starch

Cultivation of Aspergillus oryzae on starch is described as a combination of two rate processes: Starch hydrolysis and the cellular activities of the fungi including growth, enzyme production and maintenance. Kinetic models are presented to describe growth, enzyme production, starch hydrolysis and uptake of the hydrolysis products. Numerical values of the model parameters indicated that the rate controlling step of A. oryzae growth on starch was not starch hydrolysis, but the substrate uptake process. Glucose was one of the starch hydrolysis products. About 35% of the substrate consumed for biomass synthesis was glucose. Its accumulation in the medium did not cause repression of the starch hydrolysing enzymes. Steady state starch hydrolysis rates increased with initial starch concentration in the medium. Starch hydrolysing enzymes of A. oryzae have extensive industrial uses. This study may help in a more detailed understanding of the kinetic aspects of the production of these enzymes.