Immobilization of transaminases

In the previous sections, transaminases were referred as a suitable biocatalysts for the synthesis of chiral amines and amino acids. Their benefits are their wide substrate scope, high activity, and high enanho- and stereoselectivity. But some limitations in transaminase-catalyzed reachons occur as well, like product and substrate inhibition. To overcome these limitahons and to improve or alter the enzyme s properhes, enzyme immobilizahon can be the method of choice. Furthermore, to use enzymes in industrial processes, enzyme immobilizahon can 

Chitosan is a main derivative of chitin gained by N-deacetylation by treating with 40-50% NaOH, followed by several purification steps. TTie reactive amino and hydroxyl groups of chitosan make it soluble in aqueous solution at pH 6.5. The ability of chitosan as an immobilization substrate lies in its remarkable affinity to proteins, physiological inertness, nontoxicity, biocompatibility, and biodegradability [132]. 

Another alternative for co-transaminase immobilization on chitosan beads is the immobilization on catechol-chitosan-iron oxide nanoparticles. Ni et al. established a protocol for this composition carrying adhesive moieties for surface linkages [137]. After immobilization the enz3une showed higher thermal and pH stability compared to the free enz3une, and after 15 cycles of usage 50% of its activity remained. 

Immobilization on a Nickel-Nitriioacetic Acid Agarose Beads 

Another well established immobilization technique is via recombinant tags like polyhistidine tags. The idea came from immobilized metal affinity chromatography (IMAC) for the purification of proteins tagged with polyhistidine [145]. This method allows immobilization without prepurification steps and shows no interference with the enzyme structure or function, and does not affect the secretion or folding of fusion proteins within cells [146]. 

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