Towards an in situ product recovery of bio-based 3-hydroxypropionic acid: influence of bioconversion broth components on membrane-assisted reactive extraction

BACKGROUND Bioconversion broths are complex media with microorganisms that convert substrates into products in the presence of salts and nitrogen sources and that may release biomolecules. This paper deals with the impact of bioconversion broth components on the membrane-based reactive extraction of 3-hydroxypropionic acid (3-HP) by tri-n-octylamine (TOA) in n-decanol in preparation for an in situ product recovery. The focus here is on the influence of 3-HP concentration (0.5-10 g L-1), initial pH of the solution (3-5) and presence of proteins and salts on the extraction yield and kinetics. RESULTS It was found that reducing the initial acid concentration caused an acceleration of the extraction kinetics because of a higher extent of complexation with TOA. pH effects were dramatic, as enhancing the pH from 3 to 5 decreased the extraction yield from 74% to only 5% due to acid dissociation. Proteins were shown to have negligible impact on the extraction yield and kinetics, probably because of their negligible mass transfer resistance at the liquid-liquid interface compared with the membrane. Conversely, the presence of salts (potassium chloride and potassium biphosphate) was highly detrimental. The decrease in extraction yield was shown to be due to an anion exchange between the carboxylate anion of 3-HP in the organic phase and the anion of the salt in the aqueous phase. Chloride ions had more impact than biphosphate ions. CONCLUSION These results give valuable information for the implementation of a membrane-based reactive extraction as an in situ product recovery process, suggesting recommendations for bioconversion tuning. (c) 2018 Society of Chemical Industry