German scientists have metabolically engineered E. coli so that it can produce biodiesel in the form of fatty acid ethyl esters (FAEE). They expressed in E. coli, the genes for ethanol formation (derived from Zymomonas mobilis) and subsequent esterification of the ethanol with acyl groups of coenzyme A thioesters of fatty acids (from Acinetobacter baylyi ). The biodiesel product, called “microdiesel” could be produced by aerobic fermentation of the engineered E. coli in the presence of glucose and oleic acid. The main component of the FFAEs is ethyl oleate, with ethyl palmitate and ethyl palmitoleate as minor side products. In fed batch fermentations, a microdiesel concentration of 1.28 grams per liter FAEE was obtained. The FAEE constituted about 26% of the cell dry.