Growth and Respiratory Activity of Aspergillus oryzae Grown on Solid State Medium

Abstract

Growth and respiratory activity of Aspergillus oryzae KB were examined on bread medium as a model solid state medium with different combinations of water activity (Aw) of the medium and incubation temperature conditions. The growth, evaluated as to the glucosamine content of the culture, of A. oryzae KB increased logarithmically at an early incubation stage, and in spite of different Aw conditions the maximum specific growth rate was observed at 30°C and the actual maximum growth was seen at 25°C on prolonged incubation. The O₂ uptake rate increased within the logarithmic growth phase and showed a peak at an RQ value of around 1.0, followed by a parallel decrease with the RQ value. The closing stage of the logarithmic growth of A. oryzae KB coincided with the incubation period at which the O₂ uptake rate at a peak and the RQ value started to decrease. The O₂ uptake rate per unit of glucosamine was nearly constant with the same incubation temperature regardless of the Aw condition during early logarithmic growth. The O₂ uptake rates increased with increasing incubation temperature, and the maximum value for the rates was expected to be between incubation temperatures of 35 and 40°C which was higher than the optimum temperature for growth.