Direct Extraction of Propionic Acid from Propionibacterium acidipropionici Broths with Tri‐n‐octylamine

Abstract

The direct reactive extraction of propionic acid from Propionibacterium acidipropionici broths with solutions of tri‐n‐octylamine in dichloromethane, n‐butyl acetate or n‐heptane underlined the strong negative influence of the cells, due to the blockage of the interface by their adsorption. The magnitude of this effect <#>depends on the affinity of the cells for the organic phase, which is more important for n‐heptane, but only at biomass concentrations below 18 g L–1 d.w. (dry weight). Moreover, the interfacial mass transfer of the acid is also controlled by the solvent polarity, and is accelerated from n‐heptane to dichloromethane and by the addition to the organic phase of 1‐octanol as a phase modifier. The influences of the biomass concentration, the rotation speed and the solvent dielectric constant were included in a mathematical model describing the solute mass flow from the aqueous to the organic phase.

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

“…These authors suspected the adsorption of these compounds to the interface between the aqueous and the organic phases and a possible physical blockage of that interface in the presence of fermentation biomass. Similarly, Galaction et al observed a negative influence of cell adsorption to the interface on the reactive extraction of propionic acid. In our study, it would be possible that solutes and cell‐originating compounds adsorb to the organic–aqueous interface leading to mass transfer limitations.…”

Direct Extraction of Fumaric Acid from Rhizopus oryzae Suspensions—Interfacial Mass Transfer

“…As was previously reported, the yield of reactive extraction is enhanced by the addition of a more polar organic liquid in the solvent phase [ 8 , 9 ]. This effect is more pronounced for lower-polarity solvents, being the result of the improvement in the organic phase’s capacity to solve the polar molecules.…”

“…As was observed in previous studies on the direct extraction of other carboxylic acids from their specific fermentation broths, the presence of biomass significantly affects the efficiency of reactive extraction due to the following phenomena [ 7 , 9 ]: the biomass’s adsorption onto the interface separating the aqueous phase from the solvent induces the appearance of a physical barrier between the two phases, implicitly inducing an additional resistance to the interfacial transfer of the solute; the presence of biomass leads to an increase in the apparent viscosity of the aqueous phase, thus enhancing the diffusional resistance to the solute’s transfer; during the extraction process, mechanical lysis of the biomass could be produced by the shear stress generated by mixing the two phases. This phenomenon allows for the release into the aqueous phase of cytoplasmic compounds (amino acids, organic acids, or proteins) that could be co-extracted or could precipitate.…”

“…The positive influence of 1-octanol on the reactive extraction efficiency can be described by means of the amplification factor A, previously defined as the ratio between the interfacial mass flows with and without 1-octanol, respectively [ 9 ]. According to the variations plotted in Figure 6 , in all cases the factor A is over 1, confirming that the addition of 1-octanol exhibits a positive effect on the extraction efficiency, an effect that becomes more important as the solvent dielectric constant is reduced.…”

“…The experimental equipment consisted of an extraction cell of modified Lewis type previously described in [ 9 ] ( Figure 1 ). The extraction cell consisted of two compartments of 750 mL each and was made of stainless steel and glass.…”