Packed-Bed Bipolar Membrane Electrodialysis Enhances the Sustainable Conversion of l -Malic Acid from Simulated Fermentation Liquid

l -Malic acid is utilized as an effective acidifying agent and flavor modifier in the food industry. Conventional production of l -malic acid acid involves multiple steps that consume acids and bases and generate a large amount of wastewater. Bipolar membrane electrodialysis (BMED) is a cleaner alternative method for synthesizing l -malic acid acid, while the production performance (i.e., conversion efficiency and product purity) is limited by the stack configurations. Here, we initially compare two typical BMED configurations (denoted BP-C and BP-A-C) in terms of their l -malic acid acid production performances under various operating conditions. The BP-A-C is more suitable for l -malic acid acid production because its suppression of hydrogen ion leakage results in high current efficiency (87.03%). Then, to further enhance the production efficiency and overall conversion of l -malic acid acid, an emerging packed-bed BMED system was developed upon the BP-A-C. The effects of the resin type and filling method on the preparation performance were also examined. Results showed that the optimal system achieves an l -malic acid acid conversion ratio of 97.09% with an energy consumption of 6.4 kWh/kg. Economic analysis indicated that the production cost was 1.22 USD/kg. Overall, this study provides guidance for the cleaner preparation of l -malic acid acid and the design of efficient BMED methods for converting various organic acids.