Extraction and Esterification of Succinic Acid Using Aqueous Two-phase Systems Composed of Ethanol and Salts

Abstract

Succinic acid and its ester have been considered as a renewable feedstock for chemical derivatives. A biotechnological production route for succinic acid has become of interest as a sustainable alternative to the chemical route. However, its hydrophilicity makes the separation of succinic acid from the fermentation broth difficult. In this study, to recover succinic acid from the fermentation broth, an aqueous two-phase system (ATPS) composed of ethanol and salts was used, and then the extracted succinic acid was esterified with ethanol because its ester had different physico-chemical properties that helped in its purification. In the ATPS, ammonium sulfate gave the highest extractability. Succinic acid was found to be co-extracted with water to the ethanol-rich phase. In a model experiment in the absence of water, succinic acid was successfully esterified with ethanol and the kinetics obeyed a pseudo-first-order consecutive reaction. Then the esterification of succinic acid using the ethanol-rich phase after the aqueous two phase extraction was carried out. In the case of the ATPS having a high extractability, the conversion of succinic acid and the yield of the di-ester were relatively low due to the large amount of co-extracted water. It was found that the water content was a key parameter in the esterification reaction.