Abstract: Growth of Acinetobacter Sp. ATCC 31012 on various substrates and under varying conditions has been used to produce two classes of extracellular microbial protein-associated lipopolysaccharides (the "emulsans") which, on a weight-for-weight basis, are probably the most efficient emulsifiers discovered and which possess certain characteristics that permit these unique extracellular microbial lipopolysaccharides to be widely used in cleaning oil-contaminated vessels, oil spill management, and enhanced oil recovery by chemical flooding. These classes have been named .alpha.-emulsans and .beta.-emulsans, both of which have substantially the same polymer backbone but differ from each other in certain important structural aspects.