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