Table 3 Effect of nitrogen source on surface tension reduction (STR), pH, optical density (OD) and emulsification index (E24) of the mineral medium during biosurfactant production by Pseudomonas aeruginosa RS29. Results represent the mean ± SD of three independent experiments

Surface tension

62.0 ± 0.12

51 ± 0.15

36.1 ± 0.62

32.2 ± 0.3

28.9 ± 0.8

pH

7.5 ± 0.02

6.7 ± 0.5

6.8 ± 0.4

7.1 ± 0.30

7.0 ± 0.30

OD₄₆₀

0.138 ± 0.15

1.18 ± 0.03

1.39 ± 0.02

1.47 ± 0.02

1.5 ± 0.03

E24 (%)

50 ± 1.20

Surface tension

63.2 ± 0.10

35.5 ± 0.5

27.2 ± 1.0

30.9 ± 0.8

31.1 ± 0.7

pH

7.5 ± 0.03

8.2 ± 0.12

5.54 ± 0.20

8.3 ± 0.40

8.3 ± 0.45

OD₄₆₀

0.165 ± 0.05

2.33 ± 0.04

3.87 ± 0.05

4.0 ± 0.03

4.0 ± 0.04

E24 (%)

72 ± 1.0

Surface tension

62.0 ± 0.02

50.5 ± 0.15

52.2 ± 0.5

50.6 ± 0.3

47.0 ± 0.40

pH

7.5 ± 0.02

4.8 ± 0.20

4.6 ± 0.45

5.3 ± 0.4

4.8 ± 0.23

OD₄₆₀

0.162 ± 0.1

2.039 ± 0.02

2.12 ± 0.02

2.15 ± 0.04

2.15 ± 0.03

E24 (%)

36 ± 0.6

Surface tension

62.3 ± 0.05

49.3 ± 0.34

51.5 ± 0.4

52.6 ± 0.42

51.1 ± 0.50

pH

7.5 ± 0.01

5.1 ± 0.20

5.53 ± 0.2

5.0 ± 0.3

4.8 ± 0.20

OD₄₆₀

0.165 ± 0.22

1.96 ± 0.02

2.06 ± 0.01

2.12 ± 0.02

2.11 ± 0.02

E24 (%)

36 ± 0.5

Surface tension

62.2 ± 0.01

26.3 ± 0.1

26.3 ± 0.12

26.5 ± 0.1

27.0 ± 0.20

pH

7.5 ± 0.02

8.5 ± 0.10

7.4 ± 0.15

8.6 ± 0.2

8.65 ± 0.20

OD₄₆₀

0.160 ± 0.07

2.18 ± 0.01

2.36 ± 0.02

2.36 ± 0.01

2.32 ± 0.01

E24 (%)

80 ± 1.0

Surface tension

62.1 ± 0.03

26.4 ± 0.2

26.4 ± 0.4

26.5 ± 0.4

26.8 ± 0.30

pH

7.5 ± 0.03

8.3 ± 0.10

7.4 ± 0.12

8.8 ± 0.20

8.53 ± 0.30

OD₄₆₀

0.163 ± 0.2

2.08 ± 0.01

2.28 ± 0.02

2.31 ± 0.01

2.25 ± 0.01

E24 (%)

79 ± 0.6