On the basis of these results, we cannot conclude that BS29 bioemulsans
are not effective and further experimentations with different
soils and different treatment conditions are needed to
definitely assess their potential applications.
The results from soil washing experiments demonstrated that
the BS29 bioemulsans effectively remove crude oil and PAHs from
soil even though rhamnolipids were more efficient washing agent.
Several authors have demonstrated rhamnolipids are effective in
soil washing of hydrocarbons (Fortin et al., 1997; Urum et al.,
2003). In our study, the treatments were carried out adding both
the bioemulsans and rhamnolipids at the same concentration,
however the bioemulsans were a crude lyophilized extract
whereas the rhamnolipid mixture was a pure product. The active
principle accounts for 5% of the crude bioemulsans. Thus, the concentration
of the active principle is less in the BS29 bioemulsan
preparation than in the rhamnolipid one. Since a positive correlation
was found between the time of washing with the bioemulsans
and the oil removal, there is the potentiality to further increase the
treatment efficiency. Therefore, the bioemulsans produced by Gordonia
sp. strain BS29 are a very promising washing agent for the
remediation of hydrocarbon-contaminated soils.