Microbial Cell Factories BioMed Central Review Open Access Production of L-carnitine by secondary metabolism of bacteria Vicente Bernal, Ángel Sevilla, Manuel Cánovas and José L Iborra* Address: Department of Biochemistry and Molecular Biology B and Immunology, Campus of Espinardo, University of Murcia, E-30100, Spain Email: Vicente Bernal -
[email protected]; Ángel Sevilla -
[email protected]; Manuel Cánovas -
[email protected]; José L Iborra* -
[email protected] * Corresponding author Published: 2 October 2007 Received: 19 July 2007 Accepted: 2 October 2007 Microbial Cell Factories 2007, 6:31 doi:10.1186/1475-2859-6-31 This article is available from: http://www.microbialcellfactories.com/content/6/1/31 © 2007 Bernal et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Abstract The increasing commercial demand for L-carnitine has led to a multiplication of efforts to improve its production with bacteria. The use of different cell environments, such as growing, resting, permeabilized, dried, osmotically stressed, freely suspended and immobilized cells, to maintain enzymes sufficiently active for L-carnitine production is discussed in the text. The different cell states of enterobacteria, such as Escherichia coli and Proteus sp., which can be used to produce L- carnitine from crotonobetaine or D-carnitine as substrate, are analyzed. Moreover, the combined application of both bioprocess and metabolic engineering has allowed a deeper understanding of the main factors controlling the production process, such as energy depletion and the alteration of the acetyl-CoA/CoA ratio which are coupled to the end of the biotransformation.