Bioreduction

Bioreduction has emerged over the years as an alternative method to organic synthesis for the generation of chiral precursors of commercial interest. Bioreductions operate under mild conditions of pH and temperature with the help of highly regio- and enantio-selective oxidoreductase enzymes.In this contribution, the different oxidoreductase families involved in bioreductions are exemplified and their main characteristics are presented. The wide spectrum of oxidoreductase substrates (including ketones, diketones, ketoesters, aldehydes, alkenes, and keto acids) is discussed and both preparative and industrial scale examples are reported. The advantages and disadvantages of using isolated enzymatic systems versus whole-cell systems for bioreduction are discussed in terms of cost, specificity, stereoselectivity, and cofactor regeneration. The contribution is also reviewing strategies for improving the biocatalyst at the cell or enzyme level, which include process engineering, metabolic engineering as well as structure-based and nonstructure-based enzyme engineering. Finally, the potential role of metagenomics for isolating novel biocatalysts from different environments is discussed