Screening, Isolation and Molecular Characterization …
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Table 1 Screening results for biosurfactant producing bacterial isolates
Sr.
No.
Bacterial
Isolates
Emulsion
height
(cm)
Total
liquid
height
(cm)
Emulsification
index (%)
Oil
displacement
activity
Color
observed
(Hemolysis)
Type of
hemolytic
activity
1
PCB*1
0.20
1.20
16.67
+
Green
α
Hemolysis
2
PCB2
0.30
1.30
23.00
+
Yellow
β
Hemolysis
3
PCB3
0.25
1.15
21.74
++
Green
α
Hemolysis
4
PCB4
0.25
1.20
20.83
+
Yellow
β
Hemolysis
5
PCB5
0.30
1.20
25.00
+
Green
α
Hemolysis
6
PCB6
0.20
1.25
16.00
+
Green
α
Hemolysis
7
Serratia
marcescens
(This
study)
0.30
1.40
21.43
++
Green
α
Hemolysis
8
PCB8
0.30
1.20
25.00
+
Yellow
β
Hemolysis
9
PCB9
0.25
1.35
18.52
+
Yellow
β
Hemolysis
10 PCB10
0.30
1.40
21.74
++
Yellow
β
Hemolysis
*PCB- Petrol chemical bacteria
biosurfactant producing bacteria among the ten bacterial isolates. Among the studied
strains, the highest emulsification index of 25 obtained in the two isolates, namely
PCB5 and PCB8. It was also noted that the bacterial isolates PCB2, PCB3, PCB7
and PCB10 had emulsification index greater than 20. Similar range of emulsification
index reported in the literature, when tested for seven different isolates of Bacillus
sp., and Actinomyces sp., according to Bento et al. (2005) and Wang et al. (2014).
3.3 Oil Displacement Activity
Oil displacement activity helps in testing the ability of the biosurfactant to alter the
contact angle at the oil-water interface when the supernatant added to the kerosene
oil. Among the obtained results, the isolates namely PCB3, PCB7 and PCB10 showed
good oil displacement activity indicated by ++ within the ten isolated tested for oil