text: Applications in biotechnology were developed only most recently. This is due to the sensitivity of bioproducts such as proteins towards organic extractants.
  One approach by C. van den Berg et al. focuses on the use of impregnated particles for in situ recovery of phenol from Pseudomonas putida fermentations using ionic liquids. Further development led to the use of high capacity polysulfone capsules. These capsules are basically hollow particles surrounded by a membrane. The interior is completely filled with extractant and thus increases the impregnation capacity as compared to classical SIRs.
  A completely new approach of using SIRs for the separation or purification of biotechnological products such as proteins is based on the concept of impregnating porous particles with aqueous polymer solutions developed by B. Burghoff. These so-called Tunable Aqueous Polymer-Phase Impregnated Resins (TAPPIR) enhance aqueous two-phase extraction (ATPE) by applying the SIR technology. During classical aqueous two-phase extraction, biotechnological components such as proteins are extracted from aqueous solutions by using a second aqueous phase. This second aqueous phase contains e.g. polyethylene glycol (PEG). On the one hand, a low density difference and low interfacial tension between the two aqueous phases facilitate comparatively fast mass transfer between the phases. On the other hand, PEG appears to stabilize the protein molecules, which results in a comparatively low protein denaturation during the extraction. However, a significant drawback of ATPE is the persistent emulsification, which makes phase separation a challenge. The idea behind TAPPIR is to use the advantages posed by SIRs, namely low extractant loss due to immobilization in the pores and less emulsification than in liquid-liquid extraction. This way, the drawbacks of ATPE could be remedied. The setup would consist of a packed column or a fluidized bed rather than liquid-liquid extraction equipment with additional phase separation steps. Nonetheless, as yet only first feasibility studies are on the way to prove the concept. Adrawback of this method is the non-conitnous working mode. The packed column is run similar as a chromatographic column.