title: Modeling of yeast metabolism and process dynamics in batch fermentation.
abstract: Much is known about yeast metabolism and the kinetics of industrial batch fermentation processes. In this study, however, we provide the first tool to evaluate the dynamic interaction that exists between them. A stoichiometric model, using wine fermentation as a case study, was constructed to simulate batch cultures of Saccharomyces cerevisiae. Five differential equations describe the evolution of the main metabolites and biomass in the fermentation tank, while a set of underdetermined linear algebraic equations models the pseudo-steady-state microbial metabolism. Specific links between process variables and the reaction rates of metabolic pathways represent microorganism adaptation to environmental changes in the culture. Adaptation requirements to changes in the environment, optimal growth, and homeostasis were set as the physiological objectives. A linear programming routine was used to define optimal metabolic mass flux distribution at each instant throughout the process. The kinetics of the process arise from the dynamic interaction between the environment and metabolic flux distribution. The model assessed the effect of nitrogen starvation and ethanol toxicity in wine fermentation and it was able to simulate fermentation profiles qualitatively, while experimental fermentation yields were reproduced successfully as well.
authors.affiliation: Department of Chemical and Bioprocess Engineering, School of Engineering, Pontificia Universidad Católica de Chile, Casilla 306 Correo 22, Santiago, Chile.
authors.forename: Javier
authors.initials: J
authors.lastname: Sainz
authors.forename: Francisco
authors.initials: F
authors.lastname: Pizarro
authors.forename: J Ricardo
authors.initials: JR
authors.lastname: Pérez-Correa
authors.forename: Eduardo
authors.initials: E
authors.lastname: Agosin
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology; D019149:Bioreactors / Q000382:microbiology; D003198:Computer Simulation; D004734:Energy Metabolism / Q000502:physiology*; D000431:Ethanol / Q000378:metabolism; D005110:Extracellular Space / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008954:Models, Biological; D012441:Saccharomyces cerevisiae / Q000254:growth & development* / Q000378:metabolism* / Q000502:physiology; D014920:Wine / Q000382:microbiology*; D015003:Yeasts / Q000254:growth & development / Q000378:metabolism
chemical_list: D000431:Ethanol; D005947:Glucose; D005990:Glycerol