Double substrate limitation model for the bio-based production of succinic acid from glycerol

The dissolved carbon dioxide effect on succinic acid production by A. succinogenes has been investigated and a double substrate mechanistic model has been developed to describe the bioconversion of glycerol under CO2- saturated, batch systems. So far, the contribution of carbonates to the succinic acid production has only been examined in an experimental approach. In this work, the transient pH and dissolved CO2 values were used to calculate the evolution of the carbonate species in the system as well as the dynamic saturation level of CO2 that confirmed no gas-liquid limitation. The dissociation rate of MgCO3 was proved to be related to the CO2 volumetric flow rate and consequently to the growth rate. Experimental findings for glycerol concentrations ranging from 15 to 50 gL(-1) revealed no glycerol inhibition or limitation. Additionally, experiments with MgCO3 concentrations from 5 to 20( )gL(-1) have shown changes in the pH and in CO2 rates that do not affect the overall productivity. The model can predict effectively the effect of changes in initial glycerol and MgCO3 concentrations on production and consumption rates and can be used as a tool for the experimental design of continuous and scaled up systems.