Towards Cellulosic Biodiesel: Engineering Xylose and Lipid Metabolism In Yeast

The future of biofuels faces significant technological challenges to achieve sustainable and widespread use. Microbial production of biofuels seeks to address some of these issues by utilizing biological platforms which can readily be engineered for the specific task of fuel production. Engineering efforts range from the utilization of lignocellulosic materials to the overproduction of naturally-rare fuel products. The oleaginous yeast, Yarrowia lipolytica, has been growing in relevance as a platform for fatty acid-based biofuel production, naturally accumulating large amounts of triacylglycerides. As one of the more heavily studied ‘unconventional’ microorganisms, it is well equipped for implementing production pathways for yeast oil, which can be converted into biodiesel or other fatty acid derivatives. Here we show progress in using metabolic engineering to optimize the lipid accumulation pathway as well as to introduce a xylose-consuming pathway in Y. lipolytica. Higher flux towards lipid accumulation is achieved with the overexpression of two key rate-limiting steps which divert and drive flux towards lipid synthesis: acetyl-coa carboxylase (ACC) and diacylglycerol acyltransferase (DGA). Furthermore, the xylose reductase-xylitol dehydrogenase (XYL12) and xylose isomerase (XYLA) pathways are both examined for enabling pentose sugar utilization. Our findings highlight the excellent lipid production capacity of Y. lipolytica and demonstrate its promise as a platform for cellulosic biodiesel production.