(568b) Green Process Development to Crystallize Succinic Acid from Real, Low pH Fermentation Broth

Recent advancements in metabolic engineering and improved bioprocess scale-up can allow large-scale production of bio-succinic acid (SA) [1, 2]. Driven by this, few have attempted to commercialize SA bio-manufacturing with little or no success [2, 3]. Published studies emphasize low-pH fermentation and a simple and efficient downstream processing pipeline (DSP) to make SA biomanufacturing competitive [1-3]. Other studies establish that DSP contributes 70 to 80% to the overall cost of goods sold (COGS) [4, 5]. Several DSP studies for economical and sustainable recovery of SA from fermentation broth have been conducted with different unit operations such as crystallization, extraction, adsorption, membrane separation, and electrodialysis. Besides crystallization, other tested unit operations are costly, difficult to scale up, and have environmental concerns [2-6]. Crystallization is attractive since it is simple and has well-established scalability with well-understood operational parameters [6]. Various studies demonstrated the successive crystallization of SA using a designed neutral pH fermentation broth [2, 3]. The reported SA crystal purity is up to 94.2% and recovery of 80%, but the process generates waste residue and calcium salts, raising environmental and economic concerns [3-7].

Previously, we presented an end-to-end SA biomanufacturing pipeline that includes DSP to recover SA from sugarcane juice fermentation broth. The DSP scheme involves two-stage vacuum distillation and crystallization. The fermentation broth from the pilot-scale fermentation contained 63.1 g/L SA and required no acid addition; the maximum SA recovery reached 31.0% during the first stage. After stage 1, the filtrate was concentrated to 50% of its volume using vacuum distillation and subjected to stage 2 of crystallization. SA recovery from stage 2 was 47.7%. Overall, the SA recovery yield was 64.0% from the low-pH fermentation broth using two-stage vacuum distillation and crystallization. Purities of SA crystals recovered in stage 1 and stage 2 were 88.9% and 86.23%, respectively.

This study further improved the DSP for SA crystals from an actual low-pH fermentation broth. This new DSP recovers purified SA through cooling, evaporation, and antisolvent crystallization. Isopropanol (IPA) is a prominent antisolvent that can lower the solubility of SA while forming a minimum-boiling azeotrope with water. Due to this, solvent removal at low temperatures is possible through azeotropic drying. A Design of Experiment (DoE) driven approach for the anti-solvent crystallization of SA was utilized in this study. Recovery and purity measurements were used to evaluate the process. Subsequently, a statistical model was developed and validated. Overall, this process results in an SA recovery yield of >90% at purities of 95% respectively.