Modelling cell growth and polyhydroxyalkanoate (PHA) polymer synthesis by Pseudomonas putida LS46 under oxygen-limiting conditions

Polyhydroxyalkanoates (PHAs) are biodegradable, biocompatible, and non-toxic polymers synthesized by bacteria that may be used to displace some petroleum-based plastic materials. One of the major barriers to the commercialization of PHA biosynthesis is the high cost of production. Oxygen-limitation is known to greatly influence bacterial cell growth and PHA production. In this study, the growth and synthesis of medium chain length PHAs (mcl-PHAs) by Pseudomonas putida LS46, cultured in batch-mode with octanoic acid, under oxygen-limited conditions, was modeled. Four models, including the Monod model, incorporated Leudeking–Piret (MLP), the Moser model incorporated Leudeking–Piret (Moser-LP), the Logistic model incorporated Leudeking–Piret (LLP), and the Modified Logistic model incorporated Leudeking–Piret (MLLP) were investigated. Kinetic parameters of each model were calibrated by using the multi-objective optimization algorithm, Pareto Archived Dynamically Dimensioned Search (PA-DDS), by minimizing the sum of absolute error (SAE) for PHA production and growth simultaneously. Among the four models, MLP and Moser-LP models adequately represented the experimental data for oxygen-limited conditions. However, the MLP and Moser-LP models could not adequately simulate PHA production under oxygen-excess conditions. Modeling cell growth and PHA will assist in the development of a strategy for industrial-scale production.