Separation and Recovery of Penicillin in an Integrated System Containing Ionic Liquids

Abstract

An integrated process based on hydrophilic and hydrophobic ionic liquids is proposed to extract penicillin G from its fermentation broth and recover it into fresh water. With the aid of buffer salt, hydrophilic ionic liquid [C(4)mim]BF(4) (1-butyl-3-methylimidazolium tetrafluoroborate) could form an ionic liquid aqueous two-phase system (ILATPS) and extract penicillin into the ionic liquid-rich phase of ILATPS, while leaving miscellaneous proteins in the ionic liquid-poor phase. Subsequently, hydrophobic [C(4)tnim]PF(6) (1-butyl-3-methyl imidazolium hexafluorophosphate) is introduced into the ionic liquid-rich phase of ILATPS, which transfers the system into a hydrophobic ionic liquid phase in equilibrium with a water phase system (MILWS). The majority of hydrophilic [C(4)mim]BF(4) is transferred into the ionic liquid-rich phase of MILWS, leaving most of the penicillin in the conjugated water phase. The integrated ionic liquids system shows several advantages: (1) Penicillin is efficiently extracted into the ionic liquid-rich phase at neutral pH, so the protein emulsification met in the organic solvent system is avoided. (2) Hydrophobic ionic liquids could separate hydrophilic ionic liquids away from the penicillin containing aqueous phase. Consequently, the trouble for recovering the phase-forming material is overcome. Ionic liquids aggregate into cylindrical micelle in ILATPS, which leave sufficient room for transferring the substrate into the ionic liquid-rich phase. The micelles grow rapidly in MILWS. As a result, low water activity in hydrophobic ionic liquids phase leads to a low affinity with the polar penicillin and brings it back into water.