FACTORS AFFECTING SEPARATION OF ORGANIC-ACID FROM FERMENTATION BROTH BY ELECTRODIALYSIS

To predict the conditions needed for a high rate of product separation by electrodialysis in an organic acid fermentation, the effects of certain factors on the ion flux of acetic acid through an ion exchange membrane were investigated using a model fermentation broth containing acetic acid and sodium acetate. The factors examined were the flow rate, acetic acid concentration and pH of the feed solution and the glucose concentration. The ion flux decreased greatly with a decrease of the flow rate in the electrodialysis compartment to less than 0.02 m/s. The maximum flux was obtained when the feed pH was near pK(a) + 1. The experimental relationships are represented by two equations which were developed for each pH range higher and lower than a critical value, considering the dissociation and electrodialysis of acetic acid and diffusion of the hydroxyl ion. The superiority of an electrodialysis culture system with the addition of alkali to one without alkali addition is discussed.