Estimation of fungal growth in complex, heterogeneous culture

Very often, fungal fermentation processes are carried out on complex heterogeneous media, such as whole wheat flour, which are constituted of various soluble and insoluble solid particles. The measurement of the course of fungal growth during such fermentations, which are conducted in either submerged or solid state, is hindered by the presence of insoluble solid particles. The knowledge of the profile of biomass growth throughout any fermentation process constitutes an essential parameter in the estimation of kinetic variables and, subsequently, scale-up of the process. In this study, a method for the determination of fungal concentration during fermentation on whole wheat flour has been developed. The technique is based on on-line measurements of CO2 evolution during fermentation of Aspergillus awamori on whole wheat flour. Initial values for yield (YX/CO) and maintenance (mCO) coefficients were calculated from fermentations on synthetic media. Variations in impeller speed (350-550 rpm) and aeration rate (5-71/min) during fermentation caused significant effects on fungal growth. © 2002 Elsevier Science B.V. All rights reserved.