Delayed fatty acid uptake by a fatty acid secreting yeast strain with modified peroxisomal metabolism

Biodiesel, in the form of fatty acid esters, produced by oleaginous microorganisms, could represent an attractive alternative of renewable liquid biofuels. In the model yeast S. Cerevisiae lipid metabolism has been studied extensively and all genes encoding enzymes directly involved in lipid synthesis are known. In this organism exogenous long-chain fatty acids are activated to coenzyme A derivatives prior to metabolic utilization by the fatty acyl-CoA synthetases Faa1p and Faa4p. We use an FAA1,4 double mutant, that secretes free fatty acids, as a basis for metabolic engineering of this property. However, secreted fatty acids disappear late in the growth phase, presumably metabolized by the cells (1). ScPox1p is the ortholog of the human acyl-CoA oxidase 1, it catalyzes the first metabolic step of fatty acid beta-oxidation and its expression is strongly induced by fatty acids. S. cerevisiae ScPox1p null mutants are unable to grow on fatty acids as sole carbon source (2). A triple knock-out mutant faa1/4- pox1- studied in this work shows delayed uptake of the secreted fatty acids. The fatty acid production of the modified strains was analysed by optical density of the extracellular medium and gas chromatography and results are discussed. 1. Scharnewski M, Pongdontri P, Mora G, Hoppert M, Fulda M, FEBS J. 275 (2008) 2765–2778. 2. van Roermund CWT, Hettema EH, Kal AJ, van den Berg M, Tabak HF, Wanders RJA, EMBO J. 17(3) (1998) 677–687