Environmental Engineering Reference
In-Depth Information
Table 4
Growth of
Bacillus
strains on solid media com-
posed of different waste products
pheromones in the growth medium causes
expression of the srfA operon. Two types of pher-
omones are involved in the regulation in this
operon. The fi rst pheromone is ComX, which is
secreted outside the cell; when its concentration
is critical, ComP senses it and phosphorylates
itself. Phosphorylation of ComA by phosphory-
lated ComP is then observed. It activates expres-
sion of surfactin operon and ComS, which is an
ORF encoded within the srfAmRNA. In addition,
several activators (e.g. DegU) and repressors
(e.g. CodY and AbrB) are involved in ComK
activation. srf transcription is also activated by a
second pheromone CSF by inhibiting the Com-
A-phosphate phosphatise RapC (Jacques
2011
).
Bacillus
strains
T-1
Waste Products
T
′
-1
I
′
-1a
1. Whey 1
−
−
−
2. Dairy wastewater
−
++
+
3. Whey 2
−
−
−
4. Brewery effl uent 1
++
+++
+++
5. Brewery effl uent 2
+
+
+
6. Brewery effl uent 3
+++
+++
+++
7. Brewery spent grain
++
+
+
8. Sugar wastewaters
++
+
−
9. Beet pulp
+++
++++
+++
10. Molasses
++++
++++
++++
11. Soapstock 1
−
−
−
12. Soapstock 2
−
−
−
13. Oil slime
−
−
−
14. Acidic fatty wastewater 1
−
−
−
6
Unconventional
Media for Production
of Biosurfactants
by
Bacillus
Strains
15. Acidic fatty wastewater 2
−
−
−
16. Fusel
−
−
−
17. Slop*
+++
+++
+++
18. Potato decoction
++
++
++
19. Apple pomace
+
+
+
20. Citrus pomace
+
+
+
Interest in biosurfactant applications in many
industries and environmental protection has sig-
nifi cantly increased recently. However, their
large-scale application is limited due to the high
cost of production. Therefore, many efforts have
been made to reduce these costs. The success of
biosurfactant production depends on the increase
of yield, development of economical engineering
processes, and the use of low-cost effective
renewable agro-industrial substrates for their
production. The search for inexpensive raw mate-
rials is important to the overall economy of
biosurfactant production since they account for
10-30 % of the total cost (Cameotra and Makkar
1998
; Makkar et al.
2011
). The main problem in
the use of raw substrates is selection of suitable
waste materials with the right balance of nutri-
ents suffi cient for cell growth and biosurfactant
accumulation.
In our research, the potential of agro-industrial
wastes to replace synthetic media to support growth
of the
Bacillus
strains and biosurfactant synthesis
was investigated (Płaza et al.
2010
,
2011
). The
growth of bacteria was evaluated in solid and liquid
media. The results of growing
Bacillus
strains on
solid media are presented in Table
4
.
21. Fruit and vegetable
decoction
+++
+++
+++
According to Płaza et al. (
2011
)
Concentration of wastes - 100 % (v/v); * concentration of
slop - 50 %; ++++ very good growth; +++ good growth,
++ middle growth, + poor growth, − no growth
Bacillus
strains grew very well on solid media
containing two brewery effl uents, beet pulp,
molasses, slop, and a fruit and vegetable decoc-
tion. These substrates appeared to be a good
candidate to replace the conventional media,
probably due to the right balance of carbohy-
drates and lipids to support optimal growth of the
strains. Brewery effl uents, molasses, and the fruit
and vegetable decoction were then tested as sub-
strates for growth of the isolates in liquid media.
Among them, molasses, the fruit and vegetable
decoction, and brewery effl uents were found to
be the best alternative media for growth of tested
Bacillus
strains. All substrates had high values
of chemical oxygen demand (COD) and bio-
chemical oxygen demand (BOD), and nutritional
components of the wastes were effi ciently utilized
for biomass build-up. Finally, determination of
biosurfactant properties of isolates grown in
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