A dynamic model for predicting biomass and phycocyanin yields in Arthrospira (Spirulina) platensis: A guidance for effective batch cultivation

C-phycocyanin (C-PC) is a highly valuable bioproduct from the cyanobacterium Arthrospira platensis. A crucial factor affecting growth and C-PC production yield is nitrogen nutrients. In this work, an ODE-based dynamic model was constructed to simulate the effect of ammonium concentrations in a batch system on cyanobacterial growth and C-PC production. The model included dynamic regulation of the ammonium transporter and key enzymes involved in the nitrogen assimilation pathway. The prediction of C-PC production, cyanobacterial growth, and remaining ammonium concentration over 24 h strongly correlated with experimental data. Furthermore, the model was able to capture the response of genes involved in ammonium assimilation and C-PC production, as well as the primary metabolites. The dynamic interplay among ammonium, glutamine, and glutamate levels reflects the complexity of nitrogen metabolism in regulating the transcription of genes involved in ammonium uptake, assimilation, and C-PC synthesis and degradation, thus highlighting the cellular response to nitrogen stress. These findings provide a foundation for understanding these biological processes and offer a potential tool for further exploring the complex relationship between nitrogen availability and C-PC accumulation in A. platensis C1 using ammonium as a nitrogen source.