Numerical model study on polyhydroxyalkanoate production by Cupriavidus necator

Abstract

Polyhydroxyalkanoates (PHAs) are biodegradable plastic synthesized by microorganisms from renewable carbon resources and they are promising substitutes for conventional fossil-fuel-based plastics due to their similar physical properties. Pure cultures of particular microorganisms are commonly used for industrial PHA production but high production costs due to requirements of sterile conditions and refined substrates hinder the mass production of PHAs. Thus, model development for PHA production by microbes is essential to investigate the PHA formation and microbial metabolisms for enhanced productivity and PHA contents. In the present study, a comprehensive numerical model has been developed and calibrated for the non-growth associated PHA production process by Cupriavidus necator. The model parameters were calibrated with 8 selected experimental studies and the simulation results show good agreement with experimental data. Two methods were used to conduct sensitivity analysis: the simple method and the overall relative sensitivity analysis method. Maximum specific residual biomass growth rate was the most sensitive parameter. The calibrated model was used to investigate fed-batch feeding strategies that optimize PHA accumulation by limited nutrient feeding in the PHA production phase. The simulation results showed limited phosphorous feeding accumulated more PHA than limited nitrogen feeding. The optimal feeding strategy was determined to be limited phosphorous feeding at 5% of initial phosphorous during the PHB production phase, yielding simulated 226.0 g/L PHB at the end of the 168-hour operation.