Experimental study and mathematical modeling of immobilized Klebsiella oxytoca for 2,3-butanediol production

A process employing calcium alginate immobilized Klebsiella oxytoca airlift bioreactor for continuous butanediol production is studied. Klebsiella oxytoca is a facultative anaerobe fermenting glucose to 2,3-butanediol which is a potentially valuable chemical feedstock. A dynamic mathematical model has been developed to simulate the operation of the continuous immobilized cell bioreactor. The model combines simultaneous diffusion and cell kinetics, as well as cell growth and maintenance/death. Bioenergetic principles, combined with mass balance and redox balance were employed to describe the anaerobic, oxygen limited and aerobic microbial rate processes. This model can predict reasonably well the dynamic of cell growth and death, glucose and oxygen consumptions, ethanol and butanediol productions as well as intraparticle radial cell distribution. The effects of glucose feed concentration, dilution rate on 2,3-butanediol concentration and productivity have been investigated experimentally. The mathematical model can predict reasonably these effects. A method has also been developed to determine the dynamic cell distribution within the calcium alginate gel bead. The procedures involve fixing, impregnating and thin sectioning of the gel bead. Sections of less than 0.5 $\mu$m can be prepared and image analysis has been applied to quantify the cell distribution. The experimentally determined radial cell distribution agrees very well with the mathematical simulations.