Another important way to lower the cost of a microbial oil is to use inexpensive carbon sources in place of glucose. To this end, Y. lipolytica has been metabolically engineered to improve its performance in fructose and glycerol , and to permit growth in sucrose , cellobiose , starch , and inulin. Unfortunately, Y. lipolytica is unable to fully use the most abundant and inexpensive carbon source in nature, lignocellulose material. Economic conversion of lignocellulose requires use of both pentose, mainly xylose, and hexose sugars.