The Substrate Carbon Consumption and Metabolite Production to Describe the Growth of Geotrichum candidum and Penicillium camemberti on Glucose and Amino Acids

Amino acids had previously been characterized based on their ability to be assimilated as carbon sources by Penicillium camemberti and Geotrichum candidum. For each microorganism, three groups of amino acids have been characterized, leading to four different metabolic behaviours. To describe those recorded during P. camemberti growth on an amino acid and glucose, an unstructured model had previously been developed, based on the sequential consumption of both carbon substrates; glucose first, followed after its exhaustion by the selected amino acid. Only the part of the amino acid assimilated as a carbon source for cellular biosynthesis was considered in the model, which had to be deduced from the total amino acid consumption. To avoid the use of such an indirect parameter, ammonium was considered in this work, which was produced after amino acid deamination and corresponded to the release of the excess nitrogen, since amino acids contain excess nitrogen in relation to their carbon content in fungi. The model, therefore, involved substrate carbon consumption, ammonium production, as well as biomass yield on the carbon substrate, YX/S, and biomass yield on the produced ammonium, YX/P. The model proved to describe satisfactorily the various metabolic behaviours recorded during P. camemberti and G. candidum growth on an amino acid and glucose