Transfer function approach in structured modeling of recombinant yeast utilizing starch

Abstract

Compartment models are based on the division of biomass into a few pools (compartment). In this work, three biochemically structured (three-compartment, four-compartment, and eight-compartment) models are constructed to analyze anaerobic starch fermentation and growth characteristics of recombinant Saccharomyces cerevisiae. The common compartments in these models are the active compartment ( X A), the plasmid product fusion protein ( X P) and the structural part of the microorganism ( X G). Each compartment is described by a kinetic expression depending on experimental observations and studies in the literature. Parameters of the resultant kinetic model are estimated by an optimization routine. The model equations are then solved simultaneously to produce time profiles of the constructed compartments. In addition, the transfer function approach is applied to the eight-compartment model to analyze its degree of complexity in terms of the characteristic time concept. The characteristic time constants of the compartments lead to a conclusion that the eight-compartment model can be reduced to a four-compartment model. Best simulation results were obtained with the four-compartment model, confirming the results of the transfer function approach.