Proteins improved biocatalysts from engineered

In nature, enzymes play an important role in the survival and reproduction of their source organism. Therefore, many enzymes in their natural form are not suitable for application directly as biocatalysts in bioprocessing. For example, most enzymes are active at relatively mild conditions, thus may not be viable under the harsher conditions encountered in most indnstrial production systems. Various methods have been used to improve the properties of enzymes, including selectivity, activity and thermostability, in order to enable them to function as efficient industrial biocatalysts. Enzyme engineering, which encompasses rational design and directed evolution, is an efficient method to improve enzyme properties. Rational design seeks for beneficial mutations or protein sequences by applying empirically derived rules or theoretical models. Meanwhile, directed evolution uses a combinatorial approach to create libraries of enzymes from which enhanced variants can be identified... 

Although the formate/FDH system is, in principle, the most attractive for large-scale applications, the co-product carbon dioxide being very easily removed from the reaction mixture, the catalytic and operational features of native FDH enzymes are far from being optimal. In fact, they are usually characterized by a very low specific activity, limited chemical and thermal stability, and strict preference for the NADH cofactor. As these facts hamper the wide application of FDHs in the development of novel industrial synthetic processes, a huge effort has been carried out in the last years to improve the performance of this biocatalyst, mainly by protein engineering [4]. 

In this chapter, we describe development of novel enzymes including engineered PAR, LSADH, and P-keto ester reductase (KER) from P. citrinum key advances in tailoring biocatalysts by protein engineering and future aspect of them for improved bioreduction of ketones to synthesize various chiral alcohols. 

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