Reactive extraction of 3-hydroxypropionic acid from model aqueous solutions and real bioconversion media. Comparison with its isomer 2-hydroxypropionic (lactic) acid

BACKGROUND Bioconversion is a promising route to produce bio-based building blocks such as 3-hydroxypropionic acid (3-HP). Reactive extraction can be used for 3-HP recovery, and ultimately integrated to the bioconversion process. To the best of our knowledge, there is no published experimental data about the reactive extraction of 3-HP. This work aimed to study the extraction of 3-HP using tri-n-octylamine and Aliquat 336 as extractants in n-decanol. Comparison was also made with its positional isomer, lactic acid. Finally, the extraction of 3-HP from model and real bioconversion broths was examined. RESULTS The use of mixed extractants showed high performances over a wide range of experimental conditions, highlighting a synergistic effect. A possible extraction mechanism considers the formation of a ternary complex between TOA, Aliquat 336 and the carboxylic acid. When 3-HP was extracted from a real bioconversion broth, some cell-originating compounds were suspected to adsorb to the aqueous–organic interface. This effect, added to the possible competition between 3-HP and compounds that can react with the extractants, led to limitations in the yield (Y%) and selectivity (α3HP) of the extraction. For example, Y% and α3HP were respectively 89% and 35.9 for the model bioconversion broth and decreased to 62% and 15.7 for the real broth at pH = 3.2. CONCLUSION Effective experimental conditions for the reactive extraction of 3-HP were pointed out for the first time. Further work will be undertaken with a view to better elucidating the mechanisms involved in real conditions of an integrated extractive bioconversion system. © 2015 Society of Chemical Industry