Environmental Engineering Reference
In-Depth Information
group is classifi ed into four main families:
surfactins, iturins, fengycins (or plipastatins),
and (discovered in the year 2000) kurstakins.
Each family of LPs is composed of several
compounds, among which the most common are
surfactin, lichenysin A, pumilacidin, and bamylo-
cin A for the family of surfactins; iturin A and C,
bacillomycin D, F, L, and Lc and mycosubtilin
for iturins; and fengycin A and B for the fengycin
family (Jacques
2011
). In general, LPs consist of
cyclic peptides composed of seven (surfactins
and iturins) or ten (fengycins)
surface activity of tested strains or their emulsifying
ability, or cell surface hydrophobicity measure-
ment) and direct (based on the measurement of
surface/interfacial tension of a medium after
bacterial cultivation) (Fig.
1
). A new approach for
the determination of the potential ability of
Bacillus
strains for biosurfactant production is
the detection of genes encoding enzymes involved
in LP biosynthesis (Satpute et al.
2010
; Walter
et al.
2010
).
In our studies, measurement of the surface
tension, drop-collapse, oil-spreading, and blood-
agar tests were used to determine the ability of
bacilli for production of LPs when growing on
the chosen agro-industrial wastes (Table
3
).
Additionally, to confi rm the presence of genes
encoding enzymes involved in LP synthesis in
T-1, T
ʱ
-amino acids
linked to one unique
ʲ
-amino (iturins) or
ʲ
-hydroxy (surfactins and fengycins) fatty acid.
The length of this fatty acid chain may vary from
C
13
to C
16
for surfactins, from C
14
to C
17
for itu-
rins, and from C
14
to C
18
for fengycins. Different
homologous compounds for each LP family are
usually co-produced (Akpa et al.
2001
).
Because the LP biosurfactants exhibit a great
ability to reduce surface and interfacial tension,
they are excellent emulsifi ers, foaming, and dis-
persing agents widely used in many industries
such as agriculture, food production, chemistry,
cosmetics, pharmaceutics, and environmental
biotechnology (Pacwa-Płociniczak et al.
2011
).
LPs, similar to other biosurfactants, are environ-
mentally friendly, biodegradable, low toxic, and
non-hazardous. They have better foaming
properties and higher selectivity. They are active
at extreme pH and salinity conditions, but,
most importantly, they work effi ciently at high
temperatures. For example, thermotolerant
biosurfactant-producing strains of
Bacillus
(Table
to grow at temperatures up to 50 °C or even
73 °C have been successfully used in microbial-
enhanced oil recovery and oil-sludge clean-up
(Banat
1993
; Jinfeng et al.
2005
).
-1a
Bacillus
strains, the poly-
merase chain reaction with primer pairs proposed
by Tapi et al. (
2010
) and Hsieh et al. (
2004
) were
used (Fig.
1
).
The obtained results showed that strain T
′
-1, and I
′
-1
had the potential to produce three types of LPs,
i.e. fengycin, mycosubtilin/iturin, and surfactin/
lichenysin. However, this approach did not make
it possible to differentiate between mycosubtilin
and iturin, as well as surfactin and lichenysin.
In the study with the primer for the sfp gene, the
ability to produce surfactin was confi rmed only
for strain T-1. The use of primers for surfactin/
lichenysin proposed by Tapi et al. (
2010
) allowed
us to obtain a product for T
′
-1a strains
(Fig.
2
). This observation may be because, in
these two strains, surfactin is encoded by srfA
gene or they produce lichenysin only.
Mass spectrometry with electrospray ioni-
zation and nuclear magnetic resonance (NMR)
(400 MHz) were also used to characterize the
purifi ed surfactants. The preliminary chemical
analysis showed the LPs constituted rich fractions
of supernatants obtained from the cultures of
three
Bacillus
growing on molasses and brewery
effl uents. The characteristic m/z peaks of surfac-
tin, fengycin, and iturin families were observed in
the analysed samples. Also, a novel unknown
product was isolated from
Bacillus
named T
′
-1 and I
′
5
Methods for Detection
of Biosurfactant-Producing
Bacillus Strains
In general, methods used for assessment of the
bacterial biosurfactant production abilities can be
divided into indirect (involving methods of culti-
vation of bacteria on specifi c media, analysis of
-1
growing on molasses. Its chemical structure is
under evaluation by Poliwoda et al. (
2012
).
′
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