Characterization, Production, and Applications of Lipopeptides - Biosurfactants: Research Trends and Applications - page 162

was poor. Previous work by Ghojavand et al. (2008) isolated thermotolerant, halo-
tolerant, and facultative biosurfactant-producing B. subtilis strains as shown by
the 16S ribosomal deoxyribonucleic acid gene. These strains could potentially be
used for enhanced oil recovery. Another strain B. mojavensis XH1 was studied by
Li et al. (2012). A biodemulsifier was produced and isolated by ethanol extraction
and then sephadex and silicon gel column chromatography. A response surface
methodology was used to optimize the media for production. Biodemulsifier yield
increased to 2.07 g/L.
A strain of B. mojavensis (PTCC 1696) (Ghojavand et al., 2012) was isolated
from an oil field. The biosurfactant produced by the strain could reduce the surface
tension to 26.7 mN/m. Biosurfactant was added for water flooding to enhance oil
recovery from a low-permeability carbonate reservoir. Although the concentration of
the surfactant was low (0.1 g/L), it showed potential for the oil removal. Costs of the
purified surfactin for biomedical research are in the range of $10 per mg compared
to $2-$4 per kg for emulsion formulations.
A licheniformin biosurfactant was produced by B. licheniformis MS3. The lipo-
peptide contained the amino acids, Gly, Ala, Val, Asp, Ser, Gly, Tyr, and a lac-
tone ring with a fatty acid moiety at the N-terminal amino acid residue (structure).
The MW was determined as 1438 Da. The surface tension could be lowered to 38
mN/m by the isolated biosurfactant at a concentration of 15 mg/L. Isolation was per-
formed using an electroflotation column. It was stable over a range of temperatures
(45°C-85°C) and from pH 3 to 11.
Janek et al. (2010) isolated lipopeptides produced by Pseudomonas fluorescens
BD 5 from the arctic. The biosurfactants were named pseudofactin I and II. They
were cyclic with good emulsification abilities for plant oils and hydrocarbons,
comparable to that of surfactin (Abdel-Mawgoud et al., 2008). Pseudofactin II
reduced the surface tension to 31.5 mN/m with a CMC of 72 mg/L. Approximately
10 mg/L was recovered. The yield of pseudofactin I was 1/12th that of the other
form. They could potentially be used for various medical and biotechnological
applications (Figure 6.6).
A strain of B. mycoides was isolated from an oil field (Najafi et al., 2010). The
isolate produced a lipopeptide derivative that could lower the surface tension to
34 mN/m. To optimize production, a response surface methodology was employed.
Optimal production of surfactin of 3.3 g/L were obtained at 16.6 g/L glucose sub-
strate concentration, 39°C, pH 7.4, and total salt concentration of 55.4 g/L.
A response surface methodology was also employed by Wei et al. (2010) for
fengycin production. The B. subtilis F29-3 strain had been isolated from a potato
farm. The fengycin was isolated by acid precipitation at pH 2 followed by ultrafiltra-
tion and nanofiltration for purification. The media design that was optimal included
mannitol, soybean meal, sodium nitrate, and magnesium sulfate and increased pro-
duction by almost threefold (3.5 g/L).
Another strain Brevibacillus brevis (Wang et al., 2010) was isolated from an oil
field. It consisted of Asp, Glu, Val, and Leu in a ratio of 1:1:1:4 like surfactin. The
surface tension was 26.8 mN/m and the CMC was 9 × 10 −6 M. The MWs of the
various fractions varied from 1008 to 1035, depending on the C13-C15 hydrocarbon
portion. This was the first time this species was shown to produce surfactin.