Abstract
BackgroundCurrent biological pathways to produce biofuel intermediates amenable to separations and catalytic upgrading to hydrocarbon fuels are not cost effective. Previously, oleaginous yeasts have been investigated primarily for lipid production. However, yeasts store neutral lipids intracellularly making recovery difficult and expensive. In addition, once recovered from the cells, lipids are difficult to blend directly with the existing fuels without upgrading. We have, therefore, begun to investigate secreted fatty acid-derived products which can be easily recovered and upgraded to fuels.ResultsIn this study, we successfully demonstrate the production of fatty alcohols by the oleaginous yeasts, Yarrowia lipolytica and Lipomyces starkeyi, through expression of the fatty acyl-CoA reductase gene from Marinobactor aquaeolei VT8. This strategy resulted in the production of 167 and 770 mg/L of fatty alcohols in shake flask from Y. lipolytica and L starkeyi, respectively. When using a dodecane overlay during fermentation, 92 and 99% of total fatty alcohols produced by Y. lipolytica and L. starkeyi, respectively, were extracted into the dodecane phase, which compares favorably to the 3 and 50% recovered, respectively, without the dodecane layer. In both oleaginous yeasts, long chain length, saturated fatty alcohols, i.e., hexadecanol (C16:0) and octadecanol (C18:0), were predominant and accounted for more than 85% of the total fatty alcohols produced. To the best of our knowledge, this is the first report of fatty alcohol production in L. starkeyi. ConclusionThis work demonstrates that the oleaginous yeasts, Y. lipolytica and L. starkeyi, can serve as platform organisms for the production of fatty acid-derived biofuels and bioproducts.
Highlights
Current biological pathways to produce biofuel intermediates amenable to separations and catalytic upgrading to hydrocarbon fuels are not cost effective
We demonstrated that the far gene, Maqu_2220 from M. aquaeolei VT8, was successfully expressed in both Y. lipolytica and L. starkeyi and enabled the production of fatty alcohols
Production of fatty alcohols in far‐expressing Y. lipolytica Yl[fatty acyl-CoA reductase (FAR)] A well-known and commercially available YLEX expression kit was used for Y. lipolytica transformation
Summary
Current biological pathways to produce biofuel intermediates amenable to separations and catalytic upgrading to hydrocarbon fuels are not cost effective. Oleaginous yeasts have received increasing attention due to their ability to accumulate high intracellular content of neutral lipids, which are considered as alternatives to plant oils for biodiesel production [1]. Among these oleaginous species, Yarrowia lipolytica is a well-studied model organism for genetic and physiological research as well as for industrial applications [2,3,4,5]. L. starkeyi is otherwise a very attractive host species, due to its high lipid content (~60%) [13] and ability to utilize biomass-derived sugars, including glucose, xylose, mannose, and galactose [14, 15] These features make L. starkeyi a unique species for developing biofuels. With the very recent development of a transformation protocol [16], genetic engineering enables L. starkeyi to serve as unique oleaginous yeast for further biofuel research
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