L-lactic acid production using immobilized Rhizopus oryzae in a three-phase fluidized-bed with simultaneous product separation by electrodialysis

Abstract

The experimental apparatus for the simultaneous L-lactic acid fermentation by Rhizopus oryzae immobilized in calcium alginate beads and product separation process was set up in which a three-phase fluidized-bed bioreactor was used as a fermentor and an external electrodialyzer as a separator, and a pump was applied to recycle the fermentation broth between the bioreactor and the separator. The L-lactic acid produced in the fermentor was separated in the separator, product inhibition was alleviated without any addition of alkali or alkali salts and the product purification process could be simplified. The specific productivity and the yield in electrodialysis fermentation (ED-F) process operated in continuous feeding mode were almost the same as that in CaCO3-buffered fermentation process. A mathematical model of L-lactic acid production in ED-F process was also suggested, in which the model equations for the bioreactor and the electrodialyzer were combined to describe the simultaneous fermentation and product separation. The model predictions were in good agreement with the experimental data.