Production of lipopeptide biosurfactants by Bacillus atrophaeus 5-2a and their potential use in microbial enhanced oil recovery

Table 2 Dry cell weight (g L⁻¹), crude biosurfactant yield (g L⁻¹), oil spreading (cm), emulsification index (%), and surface tension (mNm⁻¹) obtained for Bacillus atrophaeus 5-2a grown in mineral salt solution with different nitrogen sources at 30 °C for 5 days

Nitrogen source	Dry cell weight (g L⁻¹)	Crude biosurfactant yield (g L⁻¹)	Oil spreading (cm)	Emulsification index (%)	Surface tension (mN m⁻¹)
Beef extract	0.64 ± 0.021e	0.47 ± 0.014c	16.5 ± 0.10f	59.50 ± 0.34c	27.64 ± 0.028b
Peptone	0.87 ± 0.057d	0.66 ± 0.028ab	18.8 ± 0.10b	59.47 ± 0.36c	26.65 ± 0.057d
Corn steep liquor	0.63 ± 0.028e	0.42 ± 0.085c	14.2 ± 0.16 g	10.41 ± 0.57d	29.51 ± 0.035a
Urea	0.99 ± 0.028c	0.78 ± 0.028a	19.2 ± 0.10a	60.54 ± 0.38ab	26.43 ± 0.021e
NH₄Cl	1.41 ± 0.014a	0.55 ± 0.071bc	16.9 ± 0.10e	59.34 ± 0.18c	27.64 ± 0.014b
(NH₄)₂SO₄	1.22 ± 0.014b	0.66 ± 0.085ab	17.2 ± 0.12d	61.16 ± 0.25a	27.42 ± 0.092c
NaNO₃	0.85 ± 0.0071d	0.73 ± 0.042a	17.6 ± 0.12c	61.23 ± 0.59a	27.38 ± 0.099c
KNO₃	0.47 ± 0.014f	0.53 ± 0.099bc	16.7 ± 0.16e	60.14 ± 0.19bc	27.60 ± 0.057b

Values are presented as the mean ± standard deviation (n = 3). Different superscript letters within a column indicate significant differences (P < 0.05) by Duncan’s multiple range test

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