초록
<P><B>Abstract</B></P> <P>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 CO<SUB>2</SUB>-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 CO<SUB>2</SUB> values were used to calculate the evolution of the carbonate species in the system as well as the dynamic saturation level of CO<SUB>2</SUB> that confirmed no gas-liquid limitation. The dissociation rate of MgCO<SUB>3</SUB> was proved to be related to the CO<SUB>2</SUB> volumetric flow rate and consequently to the growth rate. Experimental findings for glycerol concentrations ranging from 15 to 50 gL<SUP>−1</SUP> revealed no glycerol inhibition or limitation. Additionally, experiments with MgCO<SUB>3</SUB> concentrations from 5 to 20 gL<SUP>−1</SUP> have shown changes in the pH and in CO<SUB>2</SUB> rates that do not affect the overall productivity. The model can predict effectively the effect of changes in initial glycerol and MgCO<SUB>3</SUB> concentrations on production and consumption rates and can be used as a tool for the experimental design of continuous and scaled up systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We develop a new experimentally validated double-substrate succinic acid fermentation model. </LI> <LI> The model accounts for multi-phase mass transfer phenomena in the fermentation medium. </LI> <LI> Mass transfer effects of solid MgCO3 on the fermentation system are quantified. </LI> <LI> System dynamics including liquid and gaseous substrates are successfully predicted. </LI> <LI> Model can be used to design batch, continuous and scale-up fermentation systems. </LI> </UL> </P>