The name surfactin refers to a bacterial cyclic lipopeptide, primarily reno
wned for its exceptional surfactant power since it lowers the surface tensi
on of water from 72 mN m(-1) to 27 mN m(-1) at a concentration as low as 20
mu M. Although surfactin was discovered about 30 years ago, there has been
a revival of interest in this compound over the past decade, triggered by
an increasing demand for effective biosurfactants for difficult contemporar
y ecological problems. This simple molecule also looks very promising as an
antitumoral, antiviral and anti-Mycoplasma agent. Structural characteristi
cs show the presence of a heptapeptide with an LLDLLDL chiral sequence link
ed, via a lactone bond, to a beta-hydroxy fatty acid with 13-15 C atoms. In
solution, the molecule exhibits a characteristic "horse saddle" conformati
on that accounts for its large spectrum of biological activity, making it v
ery attractive for both industrial applications and academic studies. Surfa
ctin biosynthesis is catalysed non-ribosomally by the action of a large mul
tienzyme complex consisting of four modular building blocks, called the sur
factin synthetase. The biosynthetic activity involves the multicarrier thio
-template mechanism and the enzyme is organized in structural domains that
place it in the family of peptide synthetases, a class of enzymes involved
in peptidic secondary-metabolite synthesis. The srfA operon, the sfp gene e
ncoding a 4'-phosphopantetheinyltransferase and the comA regulatory gene wo
rk together for surfactin biosynthesis, while the gene encoding the acyltra
nsferase remains to be isolated. Concerning surfactin production, there is
no indication whether the genetic regulation, involving a quorum-sensing me
chanism, overrides other regulation factors promoted by the fermentation co
nditions. Knowledge of the modular arrangement of the peptide synthetases i
s of the utmost relevance to combinatorial biosynthetic approaches and has
been successfully used at the gene level to modify the surfactin template.
Biosynthetic and genetic rationales have been described for building varian
ts. A fine study of the structure/function relationships associated with th
e three-dimensional structure has led to the recognition of the specific re
sidues required for activity. These studies will assist researchers in the
selection of molecules with improved and/or refined properties useful in oi
l and biomedical industries.