Screening and identification of Pseudomonas aeruginosa AB4 for improved production, characterization and application of a glycolipid biosurfactant using low-cost agro-based raw materials

BACKGROUND: The study is focused on (i) screening and taxonomic identity of a bacterial strain for biosurfactant production, and (ii) evaluation of its potential for production of a biosurfactant using agro-based feedstock(s) and characterization of it for application in the removal of heavy metals. RESULTS: The production of biosurfactant by an isolate Pseudomonas aeruginosa AB4 (identified on the basis of 16S rRNA analysis) using various cost-effective substrates were examined at conditions 40 °C, 120 rpm for 7 days. It revealed maximum (40 gL⁻¹) rhamnolipids production and 46% reduction of initial surface tension. Its optimum production was achieved at (i) C:N ratio 10:0.6, (ii) pH 8.5 and (iii) 40 °C. The cell-free supernatant examined for biosurfactant activity by (i) haemolytic assay, (ii) CTAB- methylene blue assay, (iii) drop collapse test, (iv) oil spreading technique and (v) EI 24 assay showed its glycolipid nature and stable emulsification. Analysis of partially purified rhamnolipids by (i) thin layer chromatography (TLC), (ii) high performance thin layer chromatography (HPTLC), (iii) high performance liquid chromatography (HPLC), (iv) Fourier transform infrared (FT-IR) and (v) gas chromatography-mass spectrometry (GC-MS) confirmed its structure as methyl ester of 3-hydroxy decanoic acid (a glycolipid) with two major structural congeners (Rha-C₁₀-C₁₀ and Rha-C₁₀-C₈) of mono-rhamnolipids. Finally, it showed sequestration of Cd and Pb, suggesting its application in biosurfactant-assisted heavy metal bioremediation. CONCLUSION: This work has screened and identified a bacterium with superior biosurfactant production capabilities, characterized the glycolipidic biosurfactants as rhamnolipid and indicated the feasibility of biosurfactant production using novel renewable, relatively inexpensive and easily available resources such as non-edible vegetable de-oiled seed cakes and showed its utility in remediation of heavy metals. Copyright