Findings: The team ascertained that precipitation of
the cocktail at a pH of between one and two resulted
in maximum recovery of the antifungal lipopeptides
(78% for fengycin and 67% for iturin); it was marginally
higher than at pH 3. However, optimal purity was
obtained at pH 3 (64% for fengycin, and 3% for iturin),
thus establishing pH 3 as the preferred condition.
Dr Vivek Rangarajan adapted
the method of thin layer
chromatography (TLC) to
the measurement of the
lipopeptides fengycin, iturin
and surfactin. Compared
A LITTLE TLC GOES A LONG WAY
to high performance liquid
Dr Vivek Rangarajan adapted
the method
chromatography
(HLCP)
that
of thin layer chromatography (TLC) to the
takes two hours to process one
measurement of the lipopeptides fengycin, iturin
sample,
Vivek’s
TLC
method
and surfactin.
Compared
to high
performance
processes
20
samples
only
liquid chromatography (HLCP) that in takes
two minutes.
hours to process
one sample,
Vivek’s
45
It saves
time
and
TLC
method
processes
20
samples
in
only
45
money, and delivers the desired
minutes. It saves time and money, and delivers
indicative results.
the desired indicative results.
Lipids
Surfactin
They found that among all the organic solvents that
could remove lipid and protein impurities from the
antifungal lipopeptides, methanol proved to be most
efficient, showing 100% extraction and the highest
percentage purity (74%) of antifungal lipopeptides.
Figure 1: Bioproducts effective against pathogens
Figure 1: Bioproducts effective against pathogens
Antibacterial
Surfactin
Bacillus
lipopeptides
Antiviral
Antitumoril
Iturin A Antifungal
Fengycin Antifungal
About 100 homologues with combined broad spectrum activity
AgriKultuur |AgriCulture
CF-MeOH
“Even if the lipopeptide cocktail is not pure, it can
still be very effective,” says Prof. Clarke. “Cocktails of
varying purities will have different applications. A less
pure product could be applied to agricultural crops in
general, while a purer product could be required for
specific phytopathogens affecting fruit in post-harvest
storage.”
Fengycin
To reduce the pH of the supernatant, acid (four pH
levels) was added to the filtered Bacillus culture
to trigger the precipitation of the lipopeptides.
Eleven different solvents were also added to the
filtered Bacillus culture to affect concentration and
purification.
A LITTLE TLC GOES A LONG
WAY
Identify and quantify appropriate antifungal
lipopeptide concentration and purification
procedures:
Having determined how to produce the maximum
yield, the team’s focus shifted to finding a way to
improve the efficacy of the lipopeptide cocktail by
concentrating and purifying the product through acid
precipitation and solvent extraction.
Evaluate the effectiveness of
different lipopeptides in various
grades of purity on target plant
phytopathogens targeting the fruit
industry:
The team tested the efficacy of
the partially purified and purified
lipopeptide cocktails against various
fungal phytopathogens.
Findings: Some of the most aggressive
and destructive plant pathogens,
Botrytis cinerea, Alternaria brassicicola
and Rhizopus stolonifer, Monilinia
fructigena, Penicillium expansum and
Aspergillus sclerotiorum affecting
fruit post-harvest, were used to
43