The biosurfactant synthesized by P. aeruginosa 19SJ are most probably a mixture of rhamnolipids, the amphiphilic surface-
active glycolipids usually secreted by P. aeruginosa. Accordingly, this strain formed halos on blue agar plates,which detect the production of extracellular anionic glycolipids by Pseudomonas spp. Overproduction of biosurfactants
on mannitol occurred as the cells ceased to grow. This was expected, since growth-limiting conditions are required for
production of rhamnolipids by P. aeruginosa.