Salting-out extraction of 3-hydroxypropionic acid with reactive extraction and aqueous two-phase systems

Abstract

3-Hydroxypropionic acid (3-HP) is an isomer of 2-hydroxypropionic acid (2-HP) and an important platform molecule. A biological production route of 3-HP has become of interest as a sustainable alternative to the chemical route. However, its hydrophilic property makes the separation of 3-HP from the fermentation broth difficult. In this study, reactive solvent extraction and an aqueous two phase system (ATPS) were utilized to extract 3-HP from an aqueous solution. In the reactive extraction system, synergism, which was found in the reactive extraction of 2-HP, was not observed with mixed extractants of TBP and TOA diluted in heptane. TOA diluted in 1-octanol gave the highest extractability in the reactive extraction system. There was little effect on the extractability of 3-HP by the addition of salt to the system. In an ATPS composed of alcohols and salts, binodal curves and tie lines were measured, and then 3-HP was extracted with the ATPS. The highest extractability and distribution ratio were obtained by using an ATPS composed of t-BuOH and Na2SO4. The maximum distribution ratios in both systems were similar.