Surfactant structure effects in protein separations using nonionic microemulsions

Abstract

In this article, the extraction of cytochrome c utilizing various nonionic surfactant microemulsions has been tested to determine the effect of surfactant structure on protein partitioning. Surfactants tested include a linear alcohol ethoxylate (Neodol 91-2.5), two alkyl phenol ethoxylates (lgepal CO-520, Trycol 6985), and a series of alkyl sorbitan esters that are either ethoxylated (Tweens) or un-ethoxylated (Spans). Initial attempts to extract hemoglobin into Neodol 91-2.5 Winsor II microemulsions (oil-continuous) appeared successful based on heme estimation. Careful analysis showed that the hemoglobin had dissociated prior to extraction and that only the heme was extracted with false positive results. In fact, Neodol 91-2.5 microemulsions were unable to extract a variety of proteins with differing biophysical properties. Among all the other nonionic surfactant microemulsions tested only those made using sorbitan esters extracted significant amounts of cytochrome c. The partition coefficients achieved in this study are more than an order of magnitude higher than that seen previously in the literature for comparable sorbitan systems. However, this partition coefficient is extremely sensitive to ionic strength. At an ionic strength as low as 0.001 M, the partition coefficient is reduced to that seen in previous studies. We have found that protein partitioning in sorbitan ester microemulsions is not a function of water content. In addition, extraction is not a function of either alkyl chain length, or polyethylene oxide molecular weight. Hence, the sorbitan group appears to have an important role in extraction, possibly through a weak electrostatic protein-surfactant interaction. (c) 1995 John Wiley & Sons, Inc.

Enrichment behavior of immunoglobulin by foam fractionation using response surface methodology

“…However, reverse micellar extraction of proteins using anionic surfactant and isooctane as a solvent has received some attention [CABRAL and AIRES-BARROS 1993, HONG, et al 2000, NISHIKI, et al 1998, VASUDEVAN, et al 1995, WOLL, et al 1989]. …”

A metal‐chelate affinity reverse micellar system for protein extraction

“…Span 80 (MW ¼ 429, HLB ¼ 4.3) has a long hydrophobic tail, so it may not form reverse micelles 17,38 or form reverse micelles of very low water contents, similar to Span 60 (HLB ¼ 4.7). 20 By contrast, Triton X-45 (MW ¼ 426, HLB ¼ 10.0) have a high HLB value so it has higher aqueous solubility and does not form stable reverse micelles in organic phase.…”

“…There are several requirements for the usefulness of reverse micellar system in bioseparations, 38 and two major ones should be considered at first. The first one is the good microemulsion phase behavior characteristics that facilitate the separation process including ease of macroscopic phase separation and phase stability.…”

Thermally Responsive Reversed Micelles for Immobilization of Enzymes

“…[10,15] Therefore, nonionic surfactants such as Tween 85 have been added as a co-surfactant to decrease the interface charge density and the hydrophobicity of the ionic reversed micelles. [13,14,16] Although the micelles formed from nonionic surfactants were also reported to provide the high activity and stability of enzymes, [17] co-surfactants are necessary for the formation of the micelles. Wu et al modified AOT by inserting the hydrophilic polyoxyethylene group between the head group and the hydrophobic tail of AOT.…”