Chemical transformations of succinic acid recovered from fermentation broths by a novel direct vacuum distillation-crystallisation method

A novel alternative methodology (direct crystallisation) to the traditional calcium precipitation to obtain succinic acid (SA) from defined and wheat-based fermentation broths is reported. SA crystals were successfully recovered from fermentation broths (FB) using this method. A higher SA crystal purity (95%) and yield (70%) were obtained in the direct crystallisation method compared to a slightly modified traditional calcium precipitation method (90% and 24%, respectively). Chemical transformations (e.g. esterifications) to high-added value derivatives of both recovered SA crystals were then investigated using a range of solid acids including our acidic tunable mesoporous carbonaceous materials denoted as Starbon^® acids. Results showed that SA crystals could be successfully converted into mono- and diesters in high yields and selectivities employing solid acids regardless of the reaction conditions. The order of reactivity was found to be: pure SA crystals > SA crystals from defined FB > FB SA crystals. Results demonstrate that SA can be effectively purified from actual fermentation broths, showing the importance of integrating the fermentation and downstream processing to optimise the fermentative production of SA and its chemical transformations to produce high-added value derivatives.