Research Article Comparison of an Ion Exchanger and an In-House Electrodialysis Unit for Recovery of L-Lactic Acid from Fungal Fermentation Broth Lactic acid has long been widely used in many applications. Currently, the world- wide market is increasing due to the discovery of biodegradable polylactic acid. In this work, L-lactic acid separations from filamentous fungal fermentation broth using ion-exchange chromatography and in-house electrodialysis, were stu- died and compared. Dowex Marathon WBA was used for the lactic acid separa- tion. The adsorption equilibrium followed a Langmuir isotherm. The optimal conditions for lactic acid adsorption in a fixed-bed column were at pH 6.0, and 0.8 mL/min and elution by a mixture of 1.0 M sulfuric acid and 1.0 M phosphoric acid in a ratio of 30:70 at 0.3 mL/min. The final lactic acid recovery was 76 % with 90 % purity. A laboratory scale in-house electrodialysis apparatus was con- structed with an effective membrane area of 2.925 · 10 –3 m 2 . The effects of feeding solution concentration, flow rate, pH of the fermentation broth, and applicable voltage were studied. Under the optimal conditions, lactic acid recovery was 92 % with 100 % purity and a specific energy consumption of 0.6122 kWh/kg. Keywords: Fungal fermentation broth, In-house electrodialysis, Ion exchange chromatogra- phy, L-Lactic acid, Purity, Recovery Received: April 2, 2009; revised: May 24, 2009; accepted: June 16, 2009 DOI: 10.1002/ceat.200900125 1 Introduction Lactic acid has long been widely used in the food industry as an acidulant in food and beverage manufacturing. It has also been used as a preservative in the production of beer, jelly, cheese, dried egg white, and other food products. In addition, lactic acid can be used in the pharmaceutical and textile indus- tries [1]. To date, many attempts have focused on biodegrad- able plastic production. One such example is polylactic acid (PLA) which is manufactured by a ring-opening polymeriza- tion of a pure stereoisomer of lactic acid. PLA has a wide range of applications, e.g., it can be used for making clothes, wipes, carpet tiles, diapers, feminine hygiene products, upholstery, in- terior and exterior furniture, filtration, and agricultural prod- ucts [2]. Currently, the lactic acid market largely depends on the ex- isting applications in the food and pharmaceutical industries. However, the worldwide market for biodegradable plastics is growing by more than 20 % each year, which has substantially increased the demand for lactic acid. The worldwide consump- tion rate of lactic acid was ca. 130,000–150,000 tons per year in 1999. By the end of 2011, the global demand for lactic acid is expected to reach 200,000 tons. Lactic acid can be produced via chemical synthesis or fer- mentation [3, 4]. Currently, lactic acid bacteria, Lactobacilli, have been extensively used in lactic acid fermentation because they can synthesize the racemic mixtures of lactic acid at a high production rate. However, Lactobacilli require a complex me- dium with supplemented growth factors and amino acids. In addition, they produce both the L- and D-isomers of lactic acid. Therefore, a complicated separation is required to purify an optically pure isomer of lactic acid for polymerization [4]. Apart from Lactobacilli, Rhizopus oryzae, a filamentous fungus, is capable of producing optically pure L-lactic acid from a sim- ple medium consisting of starchy materials and pentose sugars. Thus, fungal fermentation can provide more advantageous outcomes in term of ease of the separation process and low production costs compared to bacterial fermentation [5]. Lactic acid can be separated and substantially purified from a typical fermentation broth by various separation techniques including reactive extraction [6], membrane separation [7, 8], © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim http://www.cet-journal.com Wasinee Boonkong 1 Polkit Sangvanich 2 Amorn Petsom 2,3 Nuttha Thongchul 3 1 Program in Petrochemistry and Polymer Science, Department of Chemistry, Chulalongkorn University, Bangkok, Thailand. 2 Research Center for Bioorganic Chemistry, Department of Chemistry, Chulalongkorn University, Bangkok, Thailand. 3 Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Bangkok, Thailand. – Correspondence: Dr. N. Thongchul (Nuttha.T@chula.ac.th), Institute of Biotechnology and Genetic Engineering, Chulalongkorn University, Institute Building 3, Chula 62, Phayathai, Wangmai, Pathumwan, Bangkok, 10330, Thailand. 1542 Chem. Eng. Technol. 2009, 32, No. 10, 1542–1549