HARNESSING BIOSURFACTANTS FOR SOIL BIOREMEDIATION IN THE PRESENCE OF HEAVY METALS

HARNESSING BIOSURFACTANTS FOR SOIL BIOREMEDIATION IN THE PRESENCE OF HEAVY METALS

Abstract:

In this study, bacteria were isolated from soil contaminated with waste lubricating oil, and their potential to produce biosurfactants was assessed using various methods, including oil spreading, oil drop collapse, emulsification, and blood haemolysis. Among the 45 isolates tested, 20 (44.44%) exhibited positive oil spreading, 22 (48.89%) displayed haemolytic activity (both β and α), 5 (11.11%) were capable of collapsing oil droplets within 30 seconds, and 7 (15.56%) showed strong emulsification properties. Based on these promising results and consistent activity, five isolates were selected for further investigation and identified as Pseudomonas aeruginosa MPE40, Micrococcus kristinea MPE12, Acinetobacter iwoffi MPE25, Bacillus firmus MPE30, and Pseudomonas paucimobilis MPE17.

These selected strains (MPE40, MPE30, MPE25, MPE17, and MPE12) produced biosurfactants at concentrations of 1.7g/100ml, 1.6g/100ml, 1.6g/100ml, 1.0g/100ml, and 0.8g/100ml, respectively, after 7 days of cultivation in the presence of 1% (v/v) diesel as the sole source of carbon and energy. The biosurfactants were characterized through biochemical, physical, and chemical analyses using TLC, GC-MS, and FTIR. These analyses revealed that the biosurfactants were glycolipids, primarily composed of Palmitic Hexadecanoic, Octadecanoic acid, methyl esters, and hydroxylated fatty acids linked to decanoic acid. Fourier transform infrared analysis indicated the presence of carboxyl, hydroxyl, amino, and sugar derivative groups in the surfactants. Specifically, the biosurfactants produced by these strains were named Rhamnolipid Bios-40, Firmnolipid Bios-30, Sulfoglycolipid Bios-25, Glycolipopeptide Bios-17, and Disulfoglycolipid Bios-12.

The potential of these biosurfactants for the removal of heavy metals from soil was investigated, showing a removal percentage ranging from 68.05% to 95.5% for lead (Pb) and 75.7% to 91.0% for chromium (Cr). Additionally, the pH of heavy metal-contaminated soil amended with biosurfactants was found to be lower (ranging from 5.24 to 6.71 for Pb and 4.57 to 6.21 for Cr-contaminated soil) compared to that of the original unpolluted soil (pH 6.78). This observation suggests that the biosurfactants effectively removed metals from the contaminated soil, indicating their potential for the remediation of heavy metal-contaminated soil.

Notably, Rhamnolipids Bios-40 produced by Pseudomonas aeruginosa exhibited superior metal adsorption capabilities for both lead and chromium compared to the other biosurfactants. These findings suggest that these biosurfactants hold promise as alternative remediation tools for the treatment of heavy metal-contaminated soil.

HARNESSING BIOSURFACTANTS FOR SOIL BIOREMEDIATION IN THE PRESENCE OF HEAVY METALS. GET MORE, ACTUARIAL SCIENCE PROJECT TOPICS AND MATERIALS

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