Oil displacement test
The oil displacement test is a method used to measure the
diameter of the clear zone, which occurs after dropping a
surfactant-containing solution on an oil-water interphase. The oil
displacement test was carried out according to the method of
Rodrigues et al. (2006) by adding 50 mL of distilled water to a Petri
dish with a diameter of 15 cm. After that 20 mL of diesel oil was
dropped onto the surface of the water, followed by the addition of
10 mL of culture broth supernatant. The diameter of the clear halo
on the oil surface was measured and compared with 10 mL of
distilled water as negative control.