74
C. Elizabeth Rani et al.
Table 1 Biochemical
characterization of
Pseudomonas sp.: Phenotypic
characterization of unknown
bacteria by biochemical
assays
S. No. Name of the test
Observation
Result
1
Gram’s staining
Pink rods
Positive
2
Capsule
No capsules
Negative
3
Motility test
Tumbling
movement
Positive
4
Indole test
No red ring
formation
Negative
5
Methyl red test
Yellow colour was
observed
Negative
7
Voges proskauer test No colour changes Negative
8
Citrate utilization test Persian blue
colour developed
Positive
9
Catalase test
Bubble formation
was observed
Positive
9
Oxidase test
Disc turned to
purple colour
Positive
10
Urease test
Pink colour was
developed
Positive
8.3 Production and Separation of Biosurfactant
Biosurfactant production from the selected strain was achieved and the extraction
of crude biosurfactant was done by using solvent extraction method. The solvent
mixture of chloroform: methanol (2:1) ratio had served as the appropriate proportion
for the extraction of biosurfactant. (Banat et al. 2010) reported that, chloroform and
methanol solvent mixture is a preferable procedure for the extraction of biosurfactant.
The resultant crude product was observed in the form of crystalline honey like viscous
material in the petri plates. Similarly (Dubey and Juwarkar 2001), reported that the
Pseudomonas aeruginosa produced biosurfactant was in the form of crystals. Figure 1
Showing the presence of biosurfactant in crystalline form.
8.4 Screening of Biosurfactant
8.4.1 Haemolysis Test
The haemolytic activity of the selected strain was observed. Clear zones were
thoroughly examined around the streaked areas on blood agar medium.