The surface-active properties of the produced biosurfactant
were determined for the culture broth supernatant of
B. amyloliquefaciens An6 by two conventional screening methods
(drop collapsing and the oil displacement test) and compared with
those of synthetic surfactants (Tween 80 and SDS). As seen in
Table 1, biosurfactant An6 exhibited a large area with the oil
displacement test toward diesel (115 cm2
) indicating its high surface
activity. The oil spreading test is a better predicator of biosurfactant
production because this method depends on the
decrease in water-oil interfacial tension caused by the biosurfactant
regardless of its structures (Morikawa et al., 2000). Positive results
for wetting activity were also revealed by using the drop collapse
test. These results confirmed that An6 strain is a potential producer
of surface-active molecules.