Results and discussions
3.1. Isolation and screening of biosurfactant-producing bacteria
We isolated a biosurfactant-producing strain from an oily sludge sample. The
isolate exhibited biosurfactant production based on the formation of insoluble
precipitates of ion pair in the CTAB plates because of dark blue color against the light
blue background [37]. Fig. A.1 (a) in the appendix shows that there was a dark blue
halo, which indicated that strain produced anionic biosurfactant [38]. Fig. A.1 (b)
shows that drain circle diameter of broth without cell was greater than 4 cm. It was
inferred that the isolate was a yield of biosurfactant strain [39].