| The objective of this research is to synthesize pH-degradable surfactants and investigate their use in water-in-oil microemulsion based protein extraction.; Water-in-oil microemulsions (w/o-ME's) are nanometer sized aqueous droplets dispersed in apolar solvents due to the action of surfactants. Microemulsion based protein extraction (MPE) is a quick, simple and selective method for the recovery of biornolecules. There are however four problems that limit MPE (using commercially available surfactants), namely, protein inactivation, slow or incomplete recovery of proteins, a limit to solubilization of the protein, and complete separation of the protein from the surfactant. There have been a number of approaches to solve these problems. However, this is the first approach to help resolve these issues using degradable surfactants.; Degradable surfactants are capable of splitting into non-surface active species when subjected to certain conditions depending upon their structure. Using degradable surfactants would help resolve some of these problems. After completion of the extraction process, the surfactant can be subject to conditions so that it becomes ‘surface-inactive’ and this would help separation of the surfactant from the protein. In addition the use of nonionic surfactants also contributes positively since nonionic surfactants bind less strongly as compared to ionic surfactants.; The surfactants synthesized during the course of this research comprised of polyethylene glycol (helps protein activity) as the hydrophile and a cyclic ketal as the hydrophobe. The cyclic ketal structure is susceptible to hydrolysis in the presence of mild acids. Three different surfactant systems were synthesized, with the same headgroup but different tail groups. All of them formed water-in-oil microemulsions in isooctane. The surfactants hydrolyzed (in pH 5 buffer) in an apparent zeroth order process. This is the only known research where an organic oil-soluble cleavable surfactant was synthesized, two enzymes, lysozyme and α-chymotrypsin (concentrations as high as 10 mg) could be solubilized in the microemulsions, and subsequently released within an hour with retention in enzyme activity. The phase behavior of the surfactant systems and the size of the microemulsions were also characterized and found to be consistent with that of commercially available nonionic surfactants. |
