Removal of succinic acid from fermentation broth by multistage process (membrane separation and reactive extraction)

An environmentally friendly process for separation of succinic acid from the model solutions as well as the actual post-fermentation broth left after bioconversion of raw glycerol (which is generated in a large amount as a by product during the production of biodiesel) was studied. An integrated system to realize this process was proposed which consisted of: ultrafiltration (UF), bipolar membrane electrodialysis (EDBM) and 3-step reactive extraction (RE) with commercial solvating extractants. Pre-clarification process carried out by UF allowed the removal of high molecular contaminants present in the feed solution, such as: biomass, proteins as well as bacteria cells. Significant reduction in permeate flux during the process was observed due to fouling of ceramic UF membranes. However, the fouling layer was effectively removed by applying hydraulic and chemical cleaning baths. Application of the EDBM process in the proposed integrated system allowed elimination of acidification of broth which usually generates a considerable amount of wastes. The succinic acid, present in the aqueous stream after EDBM was removed in a three-step reactive extraction at more than 90% efficiency. Extraction can support membrane techniques to separate efficiently carboxylic acids from the post-fermentation broth, however, it is not selective enough to separate succinic acid from other acids present in the broths. The only way to reach selective extraction of succinic acid over acetic, lactic acids and glycerol is to decrease pH to 2 and use Cyanex 923 as an extractant.