High-throughput Screening Methods Developed for OxidoreductasesPlease find a list of abbreviations at the end of the chapter

The interest in using enzymes as synthetic chemistry tools continues to grow rapidly [1, 2]. Among various classes of enzymes, oxidoreductases represent a highly versatile class of biocatalysts for specific reduction, oxidation and oxyfunctionalization reactions, and are currently used for the production of a wide variety of chemical and pharmaceutical products. Examples of such products include l-tert-leucine, 6-hydroxynicotinic acid, 5-methylpyrazine-2-carboxylic acid, (R)-2-hydroxyphenoxypropionic acid, and steroids [3]. Oxidoreductases are generally employed in whole-cell biotransformations or fermentation-based processes because they require expensive cofactors and coenzymes (e.g. NAD(H) or NADP(H)) to donate or accept the chemical equivalents for reduction or oxidation. To facilitate their applications in vitro, a large number of cofactor regeneration systems have been developed [4, 5]. As with most enzyme biocatalysts, the discovery and engineering of oxidoreductases with improved stability, catalytic activity, and substrate specificity are highly desirable for many applications. Thanks to recent advances in recombinant DNA technology, new enzymes can now be isolated directly from microorganisms that are difficult to cultivate by high-throughput screening of expressed libraries of environmental DNA [6], whereas improved enzymes with desired functions may be engineered rapidly by directed evolution approaches [7]. Identifying new or improved oxidoreductases by these routes requires the development of high-throughput screening methods that are sensitive, efficient, and simple to implement. This chapter focuses on various high-throughput screening methods recently developed for the discovery and directed evolution of oxidoreductases. For the purposes of this chapter, oxidoreductases have been classified into four categories: dehydrogenases, oxidases, oxygenases, and laccases. Each section begins by 77