Fabrication Of Affinity Colloidal Gas Aphrons For Protein Adsorption And Separation

Since the technology of colloidal gas aphrons (CGA) was developed in the 1970s, more attention has focused on its application in the purification of protein. It exhibited high protein recovery in protein adsorption and separation. In this work, we investigated the characterizations and applications of CGA, which are illustrated below:In this thesis, the CGA was prepared by two surfactants, AOT and Triton X-114. The effect of surfactant and salt concentration, stirring speed and time, viscosity and buffer pH on half time, gas hold and size distribution of CGA were investigated. It showed that the surfactant concentration was the most significant factor to the half time of CGA. With an increase of surfactant concentration, the half time of CGA increase rapidly, then leveling off to a plateau at the surfactant concentration higher than 1.0mg.ml-1 for AOT and 0.05ml.ml-1 for Triton X-114, respectively. The half time of CGA also increased with an increase of stirring speed up to 10,000 r.min-1, then drop gradually due to the cut effect of stirring paddle. Moreover, the salt concentration had significant influence on the CGA prepared by ionic surfactant, but had little influence on the CGA made of nonionic surfactant; pH value and viscosity had no influence on CGA.In order to obtain high selectivity in the CGA, surfactant, Triton X-114, was modified with an affinity ligand of trypsin inhibitor, p-aminobenzamidine (PAB), to synthesize the affinity surfactant (PAB-TX) and the characteristic of PAB-TX was investigated. The emulsion temperature of PAB-TX did not change compared with that of general CGA. The results showed that the affinity CGA was more stable than general CGA. The affinity CGA was applied in the purification of trypsin from the mixture of trypsin and lysozyme. The adsorption characteristics of trypsin in affinity CGA and general CGA was examined and the influence of pH on protein adsorption was discussed in detail. Due to the introduction of an affinity ligand, more trypsin were adsorbed in the CGA by affinity interaction. Compared with that of the CGA of Triton X-114, the affinity CGA showed high selective adsorption property for trypsin. In the separation of a protein mixture, trypsin and lysozyme, separation and purification factors were 1.8 and 2.5, respectively. The results exhibited that affinity CGA had higher selectivity on trypsin.