Cybernetic modeling of iron-limited growth and siderophore production.

The cybernetic modeling framework developed by Ramkrishna and co-workers has been applied to a case of bacterial metabolite production, namely the production of siderophores (iron-chelating agents) associated with iron-limiting fermentation conditions. Experimental growth data showed that, even though final biomass levels were controlled by exhaustion of the carbon source, iron-limiting conditions also affected the biomass yield. A structured model which includes the process of an iron-limiting energy resource production was able to quantitatively account for this apparent dual-substrate limitation over a wide range of batch and continuous operating conditions. The experiments data also showed quite large difference in iron uptake over the wide range of operating condition and iron levels investigated. The inclusion in the model of the processes of low and high (siderophore-mediated) affinity iron transport, and siderophore production led to simulation results that were in good quantitative agreement with the siderophore, medium and cell iron levels, in both batch and steady-state continuous culture operating conditions.