Microbial oils, produced by oleaginous microorganisms, can be used as potential alternative feedstock for biodiesel production, due to their high growth rate, non-use of arable agriculture land and fatty acid profiles similar to those derived from vegetable oilsA mixed culture of oleaginous yeast Lipomyces starkeyi and wastewater native microalgae was performed to enhance lipid and biomass production from urban wastewaters. A 400-L raceway pond, operating outdoors, was designed and used for biomass cultivation. Microalgal photosynthetic activity induced high pH and dissolved oxygen values resulted in natural bactericidal and antifungal activity. A 15% lipid/dry weight was measured at the end of the cultivation time. Fatty acid methyl ester analysis indicated that the lipids were mainly composed of arachidic acid.