Any amateur baker is familiar with the importance of yeast. This microorganism, which eats sugars and produces carbon dioxide as a byproduct in the process, leavens bread. However, the power of yeast extends far beyond bread-making. Researchers under Hal Alper, an assistant professor in Cockrell School of Engineering of The University of Texas at Austin, have managed to create a new yeast strain that can create enormous amounts of lipid from simple sugars. These lipids can be converted into fuel, potentially alleviating the approaching oil shortage.
Situated in the heart of the American oil fields, the researchers at the University of Texas at Austin derived the template for these new yeast from Yarrowia lipolytica, a common fat-producing yeast found in foods with high-oil contents such as cheeses and sausages. Ordinarily, Yarrowia is composed of 10-15 percent lipid, an extraordinary amount when compared to other microorganisms.
The uncanny ability of Yarrowia to create a large amount of lipids is due to the presence of a compound known as ATP-citrate lyase which many microorganisms lack. Through a complex series of biochemical reactions, the yeast cell is able to create a store of fatty acids accumulating glucose from the environment and storing it within the cell.
Although the Yarrowia possesses an amazing ability to convert sugars into fatty acids, the production of wild type Yarrowia is far too low for industrial purposes. Therefore, the researchers sought to improve the yield.
First, the cells are genetically modified. Some of the genes within the yeast limit fat production of the cell while others promote fat production. By removing the inhibitory genes and overexpressing the fat-promoting genes, scientists are able to boost fat production. In addition, the yeasts are subjected to abnormal conditions. Normally Yarrowia will only store large amounts of lipid during nitrogen-poor conditions. However, by rewriting the genetic code of the Yarrowia, the yeast is able to store fatty acids in normal — or even nitrogen-rich — conditions. All these factors result in a new strain of Yarrowia containing 90 percent fats.
