Preprint volume - SIBM

Pre-print Volume - Posters
VARIOUS TOPICS
Results - A total of forty-two bacterial isolates showed visible crude oil degradation.
Among them, thirteen isolates were screened for biosurfactant production. ST
reduction was displayed before appearance of the maximum emulsion value and E24
rate, which were obtained during the exponential growth phase for the majority of the
strains. All of them were able to produce emulsion, but only four strains gave more
than 20% of E24 index. Hemolytic activity on BA plates was observed for five strains.
Moreover, three strains produced dark blue halos on CTAB agar plates, thus suggesting
the anionic nature of such biosurfactants.
Based on the phylogenetic affiliation, among biosurfactant producers strains related to
Rhodococcus spp. resulted predominant, followed by Psychrobacter and Micrococcus.
Acinetobacter sp. 11/4 seemed to be the best emulsion producer as shown by both the
E24 index (43.30%) and the surface tension (21 mN/m) values. For this reason such a
strain was chosen to investigate the effect of temperature and substrate on the
biosurfactant production. During its growth with soybean oil as carbon source, the
emulsion index resulted 46.6 and 56.60% at 4 and 15 °C respectively, the highest
values recorded. Finally, Acinetobacter sp. 11/4 displayed the lowest ST values (10.9
mN/m) at 15 °C on tetradecane.
Conclusions – To date, strains belonging to the genus Acinetobacter have never been
reported as biosurfactant producer in Antarctic environment. The best combination of
stable emulsion production and surface tension reduction by Acinetobacter sp. 11/4
was shown by using soybean oil as carbon source and an incubation temperature of 4
°C.
This finding suggests that biosurfactant producer can be also isolated from Antarctica
and that they could be exploitable in bioremediation events both in their native habitat
and in other cold environments.
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