Microbial cells as catalysts for stereoselective red-ox reactions - Biotechnology Advances 2009

J.D. Carballeira, M.A. Quezada, P. Hoyos, Y. Simeó, M.J. Hernaiz, A.R. Alcantara and J.V. Sinisterra.
- Industrial Biotransformations Service, Scientific Park of Madrid, C/ Santiago Grisolía n° 2, Tres Cantos, 28760 Madrid, Spain
- Molecular Interactions Service, Scientific Park of Madrid, Faculty of Pharmacy, Universidad Complutense, 28040 Madrid, Spain
- Biotransformations Group, Department of Organic & Pharmaceutical Chemistry, Faculty of Pharmacy, Universidad Complutense, 28040 Madrid, Spain

Enzyme catalyzed reactions are commonly used at laboratory or industrial scale. Contrarily, the whole cells catalyzed reactions are restricted to special cases. The tremendous advances in the last years in Molecular Biology and more specifically in Metabolic Engineering and Directed Enzyme Evolution have opened the door to create tailor-made microorganisms or “designer bugs” for industrial purposes. Whole cells catalysts can be much more readily and inexpensively prepared than purified enzymes and the enzymes - inside the cells – are protected from the external environment and stabilized by the intracellular medium. Three situations have traditionally been considered convenient to select the use of whole cell catalyzed processes against the free enzyme catalyzed process: i) when the enzyme is intracellular; ii) when the enzyme needs a cofactor to carry out the catalytic act and iii) in the development of multi-enzymatic processes. Redox reactions represent the molecular basis for energy generation in the cell. These reactions are catalyzed by intracellular enzymes and are cofactor dependent as redox reactions need electron carriers as helpers in reduction reactions (gain of electrons) or oxidation (loss of electrons).
In this review we present an overview of the state of the art of red-ox biotransformations catalyzed by whole cells - wild-type or genetically engineered microorganisms. Stereoselective reductions, hydroxylations of arenes and unfunctionalized alkanes, alkene monooxygenation, Baeyer-Villiger reactions are among the processes described along the text, focusing in their chemo-, regio- and stereoselectivity.
Keywords: Biotransformations; Biocatalysis; Whole-cell-catalysts; Cell-factories; Designer-bugs Immobilization of cells; stereoselective reactions; red-ox reactions

http://dx.doi.org/10.1016/j.biotechadv.2009.05.001