Biological Activities, Biosorption of Heavy Metals, and Stability of Lipopeptide Biosurfactant Produced by the Alcaligenes aquatilis Bacterium YGD-2906

Abstract

Background: Biosurfactants are natural products produced by microorganisms. This study examined the antioxidant activity, biosorption of heavy metals, and stability of lipopeptide biosurfactant (BLA 2906) produced by the Alcaligenes aquatilis bacterium YGD-2906. Methods: Biosurfactant production was determined by using four techniques: hemolytic test, emulsion indices, oil spreading test, and drop collapse test. The biosorption capacity of our biosurfactant to chelate the different heavy metals. The antioxidant activity was evaluated by the reducing power, phosphomolybdate tests, and DPPH•, ABTS•+ radical scavenging assays and in the end, the stability of this biosurfactant was studied. objective: Study of the heavy metal biosorption, antioxidant activity, and stability study of lipopeptide biosurfactant BLA 2906 produced by Alcaligenes aquatilis YGD-2906. Results: A negative hemolytic test, emulsion indices of 63.11 % with crude oil, 23.66 mm of oil spreading test, and a positive drop collapse test. The lipopeptide biosurfactant BLA 2906 demonstrated its ability to chelate different heavy metals at pH = 7.2, which gave biosorption capacities of Cu (II), Fe (II), Pb (II), Cd (II), and Zn (II) of 43.34, 43.60, 50.00, 20.08 and 22.48 mg /g of BLA 2906, respectively. The total antioxidant capacity of BLA 2906 presented a value of 0.84 mg Eq Trolox / g DM for the reducing power. On the other hand, the result for the phosphomolybdate test showed a value of 1029.00 ± 3.66 μg / mL to cause a 50 % reduction of the reducing activity of the phosphomolybdenum for the BLA 2906. The result of ABTS+• scavenging activity was 10.46 %. DPPH radical-scavenging effects and BHA at varying concentrations showed that concentrations required to cause 50 % inhibition were 705.48 ± 3.89 μg / ml and 7.61 ± 0.11 μg / ml for this biosurfactant and BHA, respectively. The BLA 2906 showed high stability at different temperatures, pH, and salinity in terms of emulsification activity. Conclusion: The results obtained by the lipopeptide biosurfactant BLA 2906 are attractive to invest in future applications in different fields such as industry, environment and biotechnology.