Plastics Created From Yeast-Made Monomers

Thanks to some clever genetic engineering, chemists have developed a method to produce ω-hydroxy fatty acid monomers from yeast and turn the compounds into polymers with promising properties. Poly(ω-hydroxy fatty acids) are plastic materials with properties similar to polyethylene. But given their ester linkages, they can be easily broken down and recycled. Making the monomers via chemical synthesis, however, is prohibitively expensive. Richard A. Gross of Polytechnic Institute of New York University described how his team has genetically engineered the diploid yeast Candida tropicalis to produce commercially viable yields of ω-hydroxy fatty acids (J. Am. Chem. Soc., DOI: 10.1021/ja107707v). The yeast had previously been engineered to turn fatty acids into α,ω-diacids by oxidizing the terminal methyl group of the fatty acid chain into a carboxylic acid. Gross’s team reasoned that by eliminating the right enzymes they might be able to halt this oxidation at the alcohol stage, thereby producing ω-hydroxy fatty acids. In all, the researchers eliminated 16 genes encoding six cytochrome P450s, four fatty alcohol oxidases, and six alcohol dehydrogenases from the C. tropicalis genome. The resulting monomers were then made into poly(ω-hydroxy fatty acids), polymers with properties that fall between those of high-density and low-density polyethylene, Gross said.