Environmental Engineering Reference
In-Depth Information
antibacterial (Katz and Demain
1977
) and
antifungal (Korzybski et al.
1978
) compounds
including diffi cidin and oxydiffi cidin with wide
spectrum of antibiotic activities against aerobic
and anaerobic bacteria (Zimmerman et al.
1987
).
It has been used as a fungicide because it has the
inherent ability to colonise root systems and to
inhibit the growth of fungal plant pathogens
(Kimura and Hirano
1988
; Loeffl er et al.
1986
).
Although
B. subtilis
has been associated with
outbreaks of food poisoning (Gilbert et al.
1981
;
Kramer et al.
1982
) and human infections espe-
cially in hospitalised patients with surgical
wounds, breast cancer and leukaemia (Logan
1988
),
the exact nature of its involvement in infections
has not been established. However, a literature
review by Edberg (
1991
) revealed that
B. subtilis
does not produce signifi cant quantities of extra-
cellular enzymes or virulence factors that would
predispose it to cause infection. In addition, Ihde
and Armstrong (
1973
) reported that
B. subtilis
is
an organism with low virulence. The organism
has therefore been classifi ed as neither a human
(Edberg
1991
) nor plant (Claus and Berkeley
1986
)
pathogen. According to the National Institutes of
Health (NIH) guidelines for research involving
recombinant DNA molecules (US Department
of Health and Human Services
1986
) and the
European Federation of Biotechnology guidelines,
B. subtilis
is considered a class 1 containment
agent, and their industrial use in fermentation
processes presents low risk of adverse effects to
human health and environment.
Bacillus subtilis
produces an effective and active cyclic lipopeptide
biosurfactant known as surfactin (Cooper et al.
1987
; Peypoux et al.
1999
). Das and Mukherjee
(
2007
) reported the production of lipopeptide
surfactants by two strains
Bacillus subtilis
DM-03 and
Bacillus subtilis
DM-04 on potato
peels using both submerged and solid-state
fermentation techniques. Production of biosur-
factant with enhanced surface tension reduction
of 26 mN m
−1
and lower CMC of about 25 mg L
−1
has been reported for
B. subtilis
PT2 strain
(Pornsunthorntawee et al.
2008
). Similarly,
B.
subtilis
LB5a decreased surface tension to a
minimum value of 26.6 mN m
−1
with CMC of
33 mg L
−1
(Nitschke and Pastore
2006
). Cooper
et al. (
1981
) had earlier reported production of
lipopeptide biosurfactants by
B. subtilis
strains
with a minimum surface tension of 25 mN m
−1
and a CMC of 25 mg L
−1
. Surfactin has been
demonstrated as one of most effective biosur-
factants because of its high surface activity, effi -
ciency in bioremediation and in situ microbial
enhanced oil recovery (Mulligan
2005
; Awashti
et al.
1999
; Besson and Michel
1992
). Therefore,
the production of biosurfactants from
B. subtilis
has the potential for large-scale bio-industrial
development. Nonpathogenic lipopeptide-
producing bacteria identifi ed as
Bacillus lentus
and
B. fi rmus
have also been reported by Ibrahim
et al. (
2013
) and Joshi et al. (
2013
).
Bacillus licheniformis
is an important pro-
ducer of lipopeptide biosurfactants (Biria et al.
2010
) and has been used in industrial fermentation
processes for over a decade for the production of
several enzymes, antibiotics and special chemi-
cals (Gherna et al.
1989
; Eveleigh
1981
).
Although these
Bacillus
species have been
reported to be associated with human infections,
these occurred only in immunosuppressed indi-
viduals following trauma and other predisposing
factors. Therefore, according to the Biotechnology
Program under the Toxic Substances Control Act
under the US EPA (
1997
),
B. licheniformis
is
classifi ed as a nonpathogen and is not toxigenic.
Furthermore, the National Institutes of Health
and European Federation of Biotechnology
guidelines have also placed this organism as a
class 1 containment agent (Frommer et al.
1989
).
Nonpathogens other than
Bacillus
sp. such as
Selenomonas ruminantium
(Saimmai et al.
2013
)
and
Brevibacterium aureum
MSA13 (Kiran et al.
2010
) have also been identifi ed for the produc-
tion of lipopeptide biosurfactants.
Corynebacterium
sp. is Gram-negative,
catalase-positive, rod-shaped facultative anaero-
bic bacterium. Most members of this genus are
nonpathogenic and industrially useful as they are
known for the synthesis of amino acids, nucleo-
tides and enzymes, for the bioconversion of steroids
and for the degradation of hydrocarbons and are
used in cheese ageing (Seidel et al.
2007
; Natsch
et al.
2005
). The production of glycolipopeptide and
phospholipid biosurfactants has been reported for
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