Abstract
BackgroundProduction of valuable metabolites by Yarrowia lipolytica using renewable raw materials is of major interest for sustainable food and energy. Galactose is a monosaccharide found in galactomannans, hemicelluloses, gums, and pectins.ResultsYarrowia lipolytica was found to express all the Leloir pathway genes for galactose utilization, which encode fully functional proteins. Gene organization and regulation in Y. lipolytica resembles filamentous fungi rather than Saccharomyces cerevisiae. After Y. lipolytica was grown on mixture of glucose and galactose, it was then able to metabolize galactose, including when glucose concentrations were higher than 4 g/L. However, glucose was still the preferred carbon source. Nonetheless, a strain overexpressing the four ylGAL genes of the Leloir pathway was able to efficiently use galactose as its sole carbon source. This mutant was used to produce citric acid and lipids from galactose; the yields were comparable to or greater than that obtained for the parental strain (W29) on glucose.ConclusionsThe construction of a Y. lipolytica strain able to produce citric acid and lipids from galactose is a very important step in bypassing issues related to the use of food-based substrates in industrial applications.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0370-4) contains supplementary material, which is available to authorized users.
Highlights
Production of valuable metabolites by Yarrowia lipolytica using renewable raw materials is of major interest for sustainable food and energy
The construction of a Y. lipolytica strain that is able to produce citric acid and lipids from galactose is a very important step in bypassing issues related to the use of food-based substrates in industrial applications
Our research on the Leloir pathway of galactose utilization in Y. lipolytica has revealed that this yeast is more similar to filamentous fungi such as H. jecorina, A. nidulans, and A. niger than to S. cerevisiae and K. lactis in terms of its genetic organization and gene regulation
Summary
Production of valuable metabolites by Yarrowia lipolytica using renewable raw materials is of major interest for sustainable food and energy. Galactose is a monosaccharide found in galactomannans, hemicelluloses, gums, and pectins Compounds such as citric acid, lipids, or sugar alcohols are of industrial interest; as a consequence, using microbes such as Yarrowia lipolytica to produce them has spurred research around the world [1,2,3]. At present, research efforts are focused on using plant biomass, which contains a diversity of sugars, for the production of these valuable compounds [4]. One such sugar is d-galactose, a monosaccharide that is a C4 epimer of glucose. Galactose1-phosphate uridylyltransferase (scGAL7, YBR018C) converts this intermediate compound into UDP-galactose, simultaneously releasing glucose-1-phosphate. Because phosphoglucomutase is involved in glycogenolysis, it is not formally considered to be part of the Leloir pathway
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