Modeling PHA-producing microbial enrichment cultures--towards a generalized model with predictive power.

Polyhydroxyalkanoate (PHA) production from waste streams using microbial enrichment cultures is a promising option for cost price reduction of this biopolymer. For proper understanding and successful optimization of the process, a consistent mechanistic model for PHA conversion by microbial enrichment cultures is needed. However, there is still a lack of mechanistic expressions describing the dynamics of the feast-famine process. The scope of this article is to provide an overview of the current models, investigate points of improvement, and contribute concepts for creation of a generalized model with more predictive value for the feast-famine process. Based on experimental data available in literature we have proposed model improvements for (i) modeling mixed substrates uptake, (ii) growth in the feast phase, (iii) switching between feast and famine phase, (iv) PHA degradation and (v) modeling the accumulation phase. Finally, we provide an example of a simple uniform model. Herewith we aim to give an impulse to the establishment of a generalized model.