Assessment of formal and low structured kinetic modeling of polyhydroxyalkanoate synthesis from complex substrates

A formal kinetic mathematical model for poly-(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] terpolyester synthesis from glucose and galactose derived from whey permeate supplemented with gamma-butyrolactone by the archaeon Haloferax mediterranei was created. Further, a low structured mathematical model for poly-3-hydroxybutyrate synthesis from whey permeate by Pseudomonas hydrogenovora was developed. In both cases, biosyntheses for obtaining the experimental data used for compiling the models were performed via fed-batch cultivations. The model developed for H. mediterranei consists of 10 differential and 11 algebraic equations, including 27 kinetic constants. The model compiled for P. hydrogenovora encompasses 10 differential and 3 algebraic equations, including 36 kinetic constants. Both models were solved by Runge-Kuta variable step numerical integration with Monte Carlo parameter optimization procedure. Difficulties arising from the modeling of redirection of metabolic fluxes from biomass growth toward polyhydroxyalkanoate synthesis and byproducts are discussed.