The emulsifying activity of the biopolymers synthesized
by the selected strains grown in NB liquid medium
was detected by a modified version of the method
previously described by Cooper and Goldenberg [10].
Test tubes (10515 mm) were amended with 3.0 ml of
exopolymer diluted in distilled water (0.1%, w/v) and
3ml of a hydrophobic substrate (n-octane, xylene,
toluene, mineral oil or crude oil). Then the tubes were
shaken vigorously to homogeneity using a vortex, and
left to stand for 24 h. Emulsifying activity was expressed
as the percentage of the total height occupied by the
emulsion. The surface tension of the produced biopolymers
was measured with a Kru¨ s K11 digital tensiometer,
using a plate method [4].