Very large scale immobilized polymer

Immobilization can be achieved by adsorption or covalent fixation of the biocatalyst to a solid support (e.g. surface-modified polymer or glass beads), by entrapment or by encapsulation in gel beads (e.g., agarose, polyacrylamide, alginate, etc.). Hundreds of immobilization methods have been described and reviewed in the literature [83-89], but only a limited set of methods has found real technical applications. The first large-scale applications of immobilized enzymes were established for the enantioseparation of D- and L-amino acids by Chib-ata, Tosa and co-workers at Tanabe Seiyaku Company. The Japanese achievements in the large-scale application of immobilized systems are very well documented in an excellent multi-author publication edited by Tanaka, Tosa and Kobayashi [90] (see also section 7). Some enzyme suppliers sell important industrial enzymes not only in the free form (solution or powder) but also immobilized on solid supports. 

The costs of purification of protein polymers can be high if purification requires multiple chromatographic separations however, most repetitive protein poljuners have physicochemical properties very different from cellular proteins, and can be separated from these proteins by selective precipitation methods involving changes in temperature and pH. Similarly, protein polymers whose sequences alone may not permit such simple purification strategies can be expressed with fusion tags that facilitate purification. Secretion into the culture medium can also simplify purification and provide opportunities for less complicated large-scale syntheses, as expression hosts could be immobilized on a solid support, and protein removed in a continuous fashion without the requirement to turn over the culture entirely. 

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