Separation of lactic acid from fermentation broth by ion-exchange resin and electrodialysis

Abstract

Lactic acid has long been widely used in food, pharmaceutical, and cosmetic industries. Currently, the worldwide market is increased due to the discovery of the biodegradable polymer (polylactic acid). Lactic acid is commercially produced by fermentation of agricultural products by lactic acid bacteria or filamentous fungi. Fermentation by filamentous fungi yields optically pure L-lactic acid which is strictly required for polylactic acid synthesis. In this work, we studied and compared L-lactic acid separation from filamentous fungal fermentation broth, containing L-lactic acid, byproducts including fumaric acid, and ethanol and the remaining glucose using ino-exchange chromatography and electrodialysis. Compared with Amberlite IRA-400 and Amberlite XAD-7, Dowex Marathon WBA gave better lactic acid separation. The adsorption equilibrium followed Langmuir isotherm. The optimal condition of lactic acid adsorption was at pH 6.0, and 0.8 mL/min while the optimal condition of the desorption process was at 0.3 mL/min using mixture of 1.0 M phosphoric acid and 1.0 M sulfuric acid at the ratio of 70:30 as an eluant. The final lactic acid recovery was 76% with 90% purity. A laboratory scale single-stage electrodialysis apparatus was constructed with effective membrane area of 2.925x10[superscript-3] m[superscript2]. The effects of feed solution concentration, flow rate, pH of the fermentation broth, and applicable voltage were studied. Under the optimal condition, lactic acid recovery was 92% with 100% purity and the specific energy consumption of 0.6122 k Wh/kg.