Reverse micellar methods

Solvent displacement Salting out Emulsion diffusion Emulsion-solvent evaporation SCF technology Complexation/coacervation Reverse micellar methods In situ polymerization... 

Product recoveiy from reversed micellar solutions can often be attained by simple back extrac tion, by contacting with an aqueous solution having salt concentration and pH that disfavors protein solu-bihzation, but this is not always a reliable method. Addition of cosolvents such as ethyl acetate or alcohols can lead to a disruption of the micelles and expulsion of the protein species, but this may also lead to protein denaturation. These additives must be removed by distillation, for example, to enable reconstitution of the micellar phase. Temperature increases can similarly lead to product release as a concentrated aqueous solution. Removal of the water from the reversed micelles by molecular sieves or sihca gel has also been found to cause a precipitation of the protein from the organic phase. 

Recently however, it has been recognized that liquid extraction is a potential method in the primary recovery of fermentation cell culture products, such as proteins and amino acids. The separation problem, however, is difficult because the product mixtures are often complex, including cell debris and enzymes. Proteins are not suitable for conventional solvent extraction because of incompatibility with organic solvents, but can be handled in aqueous two-phase systems or by extraction in reverse micellar systems (Chapter 15). 

Reverse micellar extraction (RME) is another attractive LLE method for DSP of biological products, as many biochemicals including amino acids, proteins, enzymes, and nucleic acids can be solubilized within and recovered from such solutions without loss of native function/activity. In addition, these systems offer low interfacial tension, ease of scale-up, and continuous operation. RME offers a number of unique, desirable features in comparison with ATPE, which has been extensively studied ... 

An alternative to the injection method for importing enzymes into a microemulsion is the phase transfer method. In this method, a layer of an aqueous enzyme solution is located under a mixture of surfactant and oil. Upon gentle shaking, the enzyme is transferred into the reverse micelles of the hydrocarbon phase. Finally, the excess of water is removed and the hydrophobic substrates can be added. The main advantage of this method is that it ensures thermodynamically stable micro emulsions with maximum water concentrations. However, the method is very time consuming. The method is often applied in order to purify, concentrate or renaturate enzymes in the reverse micellar extraction process [54-58]. 

Methods. Z-Tyr-Gly-NH2 was synthesized from Z-Tyr-OMe and Gly-NH2 In reversed micellar solutions containing 0.15 M DTAB as the surfactant In a 1 5 volume mixture of n-hexanol and n-octane. Hexanol acts as a cosurfactant and aids In solubilizing the Z-Tyr-OMe. Initial rate kinetic studies employed the hydrolysis of the synthetic substrates GPANA and BTPNA In reversed micelles of CTAB In a... 

A further technique to overcome the mass transport limitations in biphasic catalysis is the method to work in micellar [187] or reverse micellar [188] systems, that means to enhance the surface area decisively via addition of surfactants. Ren-ken found higher reaction rates and selectivities than in non-micellar systems and could hydroformylate also olefins with a long hydrocarbon chain up to C16 (see also Section 4.5). 

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