The effect of the nitrogen source on biosufactant production is shown in Table 2. D. caeni PO5 was able to use nitrogen sources such as ammonia and urea for biosurfactant production. However, in order to obtain high concentrations of biosurfactant it is necessary to have restricted conditions for these macro-nutrients. We determined that commercial CMSG was the best source of nitrogen for growth and biosurfactant synthesis. The masimum biosufactant yield (0.28 g/l) and emulsifying activity (45.53 %) and the lowest surface tension (35.5 mN/m) were obtained in media containing CMSG. No significant change in pH was observed in this case (data not shown). A similar reslt was reported in biosurfactant isolated from Selenomonas ruminantium CT2 (Saimmai et al. 2013a).