Engineering Yarrowia lipolytica for the Production of Medium Chain Fatty Acids and Alcohols
Lipids are naturally derived molecules containing long alkyl chains that represent an attractive renewable alternative to petroleum derived products. Fatty acids can be further converted to other derivatives including (1) methyl and ethyl esters which can be used as biodiesel, (2) fatty waxes to be used in cosmetics, food, and paper industries, (3) fatty alcohols with applications as surfactants and industrial solvents, and (4) alkanes that can directly be used as fuel[1-4]. Medium chain fatty acids and their corresponding derivatives, however, more closely match the desired chemical and physical properties of widely used petroleum-based chemicals. We employed the oleaginous yeast Yarrowia lipolytica, which is capable of producing lipids to titers ~20-fold higher than traditional yeasts from sugar substrates, to produce medium chain fatty acids and alcohols[5, 6]. Five different Acyl-ACP thioesterases with specificity for medium chain fatty-acyl ACPs were expressed in Y. lipolytica resulting in production of either decanoic or octanoic acid at up to 40% of the total cell lipids.
Figure 1: Abundance of Total Lipids of specific chain length in strains of Y. lipolytica PO1f expressing five different Acyl-ACP-thioesterases
The reduction in fatty acid chain length resulted in a two-fold increase in specific lipid productivity. The yeast's native machinery was able to further modify these medium chain fatty acids and incorporate them equally into all relevant classes of lipid molecules including acyl-glycerides, esters, sterols, and free fatty acids. Furthermore, reduction in fatty acid length resulted in an overall change in the relative abundance of each lipid class.
Figure 2: Specific lipid yields of Y. lipolytica PO1f strains expressing different Acyl-ACP Thioesterases
Figure3: Abundance of each lipid class in Y. lipolytica PO1f strains expressing different Acyl-ACP Thioesterases
More than twice as much of the naturally produced sixteen and eighteen carbon fatty acids remained in the form of free fatty acids compared to the wild-type strain. Concurrent expression of a fatty acyl-CoA reductase in medium chain fatty acid producing strains resulted in the formation of the corresponding fatty alcohol.
2. Santos, T.M., A. Pinto, A.V. Oliveira, H.L. Ribeiro, C.A. Caceres, E.N. Ito, and H. Azeredo, Physical properties of cassava starch–carnauba wax emulsion films as affected by component proportions. International Journal of Food Science & Technology, 2014.
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