B. subtilis SPB1 biosurfactant production was performed
in 250-ml Erlenmeyer flasks containing 50 ml of the liquid
mineral optimized medium, described in a previous work by Mnif,
Ellouze-Chaabouni, and Ghribi (2012). At the end of the cultivation,
the culture was centrifuged at 10,000 rpm and 4 C for 20 min to
remove bacterial cells.