Characterization of pH-sensitive polymeric supports for selective precipitation of proteins

pH-sensitive polymeric supports, a submicron acrylic latex and reversibly soluble polymers have been characterized for selective precipitation of proteins. Decreasing the pH and/or increasing the ionic strength of the system can greatly enhance the precipitation of the supports. The sedimentation rate of the latex particles is much faster than that of the reversibly soluble polymer in the precipitated state. The positively charged protein, lysozyme, can be precipitated by both supports. The precipitation capacity of the reversibly soluble polymer, Eudragit L 100, is about 12 times greater than that of the latex. Al pH 6.5 and a polymer/protein mass ratio of 0.2, the percentage of lysozyme precipitated by Eudragit L 100 is very high (95%), as compared to only 7% precipitated by the latex. However, it is very difficult to recover the lysozyme precipitated by Eudragit L 100. Only 30% of the precipitated lysozyme can be recovered by dissolving the precipitate in 1 M NaCl solution (pH 9) and reprecipitating Eudragit L 100 by lowering the pH from 9 to 2. On the other hand, the precipitated lysozyme can be recovered almost completely from the latex particles by using 1 M NaCl solution.