An assessment of nonspecific adsorption to Eudragit S-100 during affinity precipitation

Protein purification by affinity precipitation

Developing the most efficient strategy for the purification of a (recombinant) protein especially at large scale remains a challenge. A typical problem of the downstream process of mammalian cell products is, for instance, the early capture of the highly diluted product from the complex process stream. Affinity precipitation has been suggested in this context. The technique is known for over 20 years, but has recently received more attention due to the development of new materials for its implementation, but also because it seems ideally suited to specific product capture at large scale. The present review gives a comprehensive overview over this technique. Besides an introduction to the basic principle and a brief summary of the historical development, the main focus is on the current state-of-art of the technique, the available materials, important recent applications, as well as process design strategies and operating procedures. Special consideration is given to affinity precipitation for product recovery at large scale.

Reversibly soluble biocatalyst: optimization of trypsin coupling to Eudragit S-100 and biocatalyst activity in soluble and precipitated forms

Eudragit S-100, a copolymer of methacrylic acid and methyl methacrylate is soluble at pH above 5 and insoluble at pH below 4.5. pH-dependent solubility of the polymer is used for the development of reversibly soluble biocatalyst, which combines the advantages of both soluble and immobilized biocatalysts. Activity of trypsin, covalently coupled to Eudragit S-100, was improved by protecting the active site of the enzyme with benzamidine and removing the noncovalently bound proteins with Triton X-100 in 0.15 M Tris buffer (pH 7.6). Accurate choice of coupling conditions combined with proper washing protocol produced highly active enzyme-polymer conjugate with no noncovalently bound protein. Two conjugates with 100-fold difference in the content of trypsin coupled to Eudragit S-100 were studied when the preparations were in soluble and precipitated forms. The K(m)values of the soluble enzyme to the lower molecular weight substrate was less than that of the free enzyme, whereas that to the higher molecular weight substrate was closer to that of the free enzyme. Activities of the soluble and precipitated immobilized trypsin with higher molecular weight substrate were completely inhibited by soy bean trypsin inhibitor, whereas complete inhibition with soy bean trypsin inhibitor was never achieved with lower molecular weight substrate, indicating reduced access of high-molecular weight substrate/inhibitor to some of the catalytically active enzyme molecules in trypsin-Eudragit conjugate.

Affinity precipitation of alpha-amylase inhibitor from wheat meal by metal chelate affinity binding using cu(II)-loaded copolymers of 1-vinylimidazole with N-isopropylacrylamide

A method for purifying alpha-amylase inhibitor from wheat meal based on immobilized metal affinity with a thermosensitive copolymer is developed. The studies represent the thermoprecipitation properties of the copolymers of N-isopropylacrylamide (NIPAM) with iminodiacetic acid (IDA) and 1-vinylimidazole (VI), respectively. The polymer which is obtained by the copolymerization of 1-vinylimidazole and N-isopropylacrylamide, charged with Cu(II), exhibited specific interaction of the metal ions to the protein inhibitor. The precipitation was induced by salt and the recovery of the amylase inhibitor was achieved by dissolving the inhibitor-polymer complex in imidazole buffer and subsequent precipitation of the polymer. A single family of the alpha-amylase inhibitor was recovered from the polymer with 89% yield and about fourfold purification. The SDS-PAGE pattern showed significant purification of the inhibitor. The binding of the inhibitor to the Cu(II)-polymer conjugate depends upon the Cu(II) concentration in the copolymer and also upon the concentration of the protein. The recovered polymer could be reused with reasonable efficiency. Copyright 1998 John Wiley & Sons, Inc.