This study was aimed at the development of economical methods for higher yields of biosurfactant by suggesting the use of low-cost raw materials. Two oil-degrading strains, Pseudomonas aeruginosa QS9-119 and DS10-129, were used to optimize a substrate for maximum rhamnolipid production. Among the two strains, the latter produced maxima of 4.31, 2.98, and, 1.77 g/L rhamnolipid biosurfactant using soybean. oil, safflower oil, and glycerol, respectively. The yield of biosurfactant. steadily increased even after the bacterial cultures reached the stationary phase of growth. Characterization of rhamnolipids using mass spectrometry revealed the presence of dirhamnolipids (Rha-Rha-C-10-C-10). Emulsification activity of the rhamnolipid biosurfactant produced by P. aeruginosa DS10-129 was greater than 70% using all the hydrocarbons tested, including xylene, benzene, hexane, crude oil, kerosene, gasoline, and diesel. P. aeruginosa.GS9-119 emulsified only hexane and kerosene to that level.