To study the effect of environmental factors on solubilization
potency, activities were evaluated at different pH, temperature and
salinity values. Regarding the effect of pH, biosurfactant-induced
solubilization reaching its optimum at pH ranging from 6.0 to
10.0 (Fig. 4A). The percentage of solubilization by biosurfactant An6
as well as the synthetic surfactants was reduced at acidic pH.
Compared with neutral pH, a significant decrease of solubilization
potency of the biosurfactant An6 at pH 3.0, 4.0 and 5.0 of approximately
43, 35 and 13%, respectively, was observed. Moreover,
when testing the effect of NaCl content on solubilization efficacy,
we showed that the maximum solubilizing activity was achieved
when 10% NaCl was added (Fig. 4B). Varying the assay temperature
had no effect on the solubilization (data not shown). The retention
of its activity at high temperature suggests that biosurfactant An6
might be useful in extreme environments.