Extractive fermentation of l-lactic acid with immobilized Rhizopus oryzae in a three-phase fluidized bed

A three-phase fluidized bed bioreactor was designed to perform the extractive fermentation of l-(+)-lactic acid by Rhizopus oryzae immobilized in calcium alginate beads. In situ extractive fermentation as well as simultaneous extraction with a coupled solvent column was investigated. The solvent selected was TRPO diluted with sulfonated kerosene. The results indicated that the pH value in the aqueous phase was regulated above 3.5 and product inhibition was alleviated. The production rate was as high as 11 g l-lactic acid/h L beads. A mathematical model of l-lactic acid production based on the mass balance was also suggested to describe the extractive fermentation processes. The model predictions are in good agreement with the experimental data.