Metabolic engineering of escherichia coli for lactic acid production from renewable resources

Abstract

Metabolic engineering has been used to develop Escherichia coli strains that generate d or l-lactic acid as the predominant fermentation product from different carbon sources, including glucose and xylose, which are present in syrups from lignocellulosic hydrolysates. As an introduction, this review presents the relevance that lactic acid has nowadays in several industrial and commercial applications. It also stresses the relevance of producing d or l-lactic acid as pure optical enantiomers for different applications. The second part reviews the metabolic engineering and adaptive evolution efforts developed with E. Coli to achieve the production of optically pure d or l-lactic acid using several carbon sources. Furthermore, a set of results using actual mixtures of sugars contained in lignocellulosic hydrolysates is presented and discussed. Even though the efficient conversion of sugars to d or l-lactic acid and high volumetric productivities has been achieved, this review reveals that most work needs to be performed with actual lignocellulosic hydrolysates at the pilot or demonstrative scales to deploy the full potential of this efforts towards industrial production.