The objective of this research is to conduct systematic engineering studies on the growth kinetics, morphology, stability, gene expression, and secretion in recombinant filamentous fungi. A recombinant Aspergillus nidulans strain has been chosen as a first system for study. It carries a glucoamylase gene under the control of the strong inducible promoter of the A. nidulans alcohol dehydrogenase I (alcA) gene. The cloned product, glucoamylase, is secreted into the medium. The alcA promoter is activated in the presence of various compounds including ethanol, cyclic alcohols, and threonine, and is subject to carbon catabolite repression. Glucoamylase expression levels can be regulated by a combination of induction-repression conditions. Experiments will be conducted with both host and recombinant cells to provide a quantitative description of the growth dynamics of recombinant fungal cells in terms of growth rates, nutrient yields, production rates, secretion efficiencies, productivities, and stabilities. This information can be used in the future to build a mathematical model of fungal growth dynamics, necessary in the engineering design and development of operational strategies for bioreactors used in the production of recombinant proteins from filamentous fungi.
