Characterization of Bacillus Strains Producing Biosurfactants - Environmental Sustainability: Role of Green Technologies - page 170

F i g . 2 Agarose gel electrophoresis of polymerase chain
reaction products of genes encoding lipopeptides in
Bacillus strains (T

(P-1, control). ( a ) - primer pairs: Af2-F/Tf1-R (fengycin),
Am1-F/Tm1-R (mycosubtilin/iturin), and As1-F/Ts2-R
(surfactin/lichenysin), ( b ) - primer pair sfp (surfactin) ′ -1, I ′ -1a, and T-1) and Pseudomonas sp.

So far, one of the most often studied genes for
the screening of the ability of Bacillus strains to
surfactin production has been sfp (Hsieh et al.
2004 ; Hassan et al. 2010 ). The new approach for
the detection of non-ribosomal peptide synthe-
tases (NRPSs) and hybrid polyketide synthetases
(PKS-NRPSs) genes coding enzymes involved in
synthesis of LPs was proposed by Tapi et al.
( 2010 ). They designed four primer pairs, named
As1-F/Ts2-R, Am1-F/Tm1-R, Ap1-F/Tp1-R, and
Af2-F/Tf1-R. The proposed approach allows the
detection of the presence of both NRPSs and
PKS-NRPSs genes in analysed bacilli (Tapi et al.
2010 ). Apart from genes responsible for biosur-
factant production, the mechanism of regulation
of the expression of the operon involved in bio-
synthesis has been intensively studied (Jacques
2011 ). It has been found that production of LPs is
a cell-density-responsive mechanism utilizing
several pheromones, ComX, PhrC, PhrG, and
PhrH, and transcription factors, such as CodY,
DegU, and AbrB. LPs of Bacillus subtilis are
synthesized by NRPSs or by PKS-NRPSs
(Ongena and Jacques 2008 ). They are known as
enzymes involved in the biosynthesis of several
hundred bioactive compounds. These synthetases
consist of functional units called modules that
catalyze the different reactions necessary in pep-
tide biosynthesis. Each module is sub-divided

into several catalytic domains responsible for
each biochemical step. A typical NRPSs module
comprises about 1,000 amino acid residues and is
responsible for one reaction cycle of selective
substrate recognition and activation (Ongena and
Jacques 2008 ; Tapi et al. 2010 ). The operons of
the surfactin family contained four open reading
frames (ORFs) coding for surfactin end licheny-
sis synthetases, which are designed srfA-A,
srfA-B, srfA-C, and srfA-D or lchA, lchB, lchC,
and lchD (Tapi et al. 2010 ). Similarly, plipastatin
or fengycin are synthesized by NRPSs by an
operon with fi ve ORFs, namely ppsA, ppsB,
ppsC, ppsD, and ppsE (fenC, fend, fenE, and
fenB). In turn, iturin molecules are synthesized
by PKS multi-modular enzymes encoded by an
operon that consists of four ORFs called fenE,
mycA, mycB, mycC, or ituD, ituA, ituB, and
ituC for mycosubtilin or iturin, respectively.
Apart from genes responsible for biosurfac-
tant production, the mechanism of regulation of
the expression of the operon involved in biosyn-
thesis is as yet completely unknown. Most have
focused on the regulation of surfactin. Production
of this biosurfactant is a cell-density-responsive
mechanism not based on homoserine lactone but
utilizing several pheromones, ComX, PhrC,
PhrG, and PhrH and transcription factors, such as
CodY, DegU, and AbrB. Accumulation of these