PARTITIONING AND PURIFICATION OF THAUMATIN IN AQUEOUS 2-PHASE SYSTEMS

The partition behavior of pure thaumatin in aqueous two-phase systems has been examined in order to investigate the effects of changes in phase components on the partition coefficient, K. Factors such as MW of PEG, pH, and concentration of NaCl (and other salts) were all found to influence K, whereas the protein concentration had no effect (up to 40 g l-1 under optimum partitioning conditions). Conditions were found in PEG/phosphate systems where the partition coefficient, K, can be increased 60 times from K = 0.53 to K = 33. The separation and purification of thaumatin from a typical protein contaminant such as those in a homogenate of E. coli cells was studied. Optimum conditions were found by studying partition conditions of the thaumatin and E. coli homogenate proteins independently. Such conditions were then used and investigated with a mixture of thaumatin and E. coli homogenate proteins using a reversed phase HPLC method to follow the concentration of thaumatin in the protein mixture.