Biosurfactants obtained from natural isolations: analyzing their properties for bioremediation of contaminated environments

LOPEZ, NANCY I.; MARIA DEL ROSARIO JACOBY; LAURA J. RAIGER IUSTMAN

San Luis

Congreso; XIII Congreso Argentino de Microbiologia General SAMIGE 2018; 2018

SAMIGE

Oil pollution is an environmental problem of increasing importance. Hydrocarbon-degrading microorganisms, adapted to grow and thrive in oil-containing environments, have an important role in the biological treatment of this pollution. One of the limiting factors in this process is the bioavailability of many fractions of the oil. The addition of surfactants as biostimulation techniques was described as Surfactant Enhanced Bioremediation, in which is habitually used non-biodegradable surfactant. Due some hydrocarbon-degrading microorganisms produce biosurfactants of diverse chemical nature and molecular size, the aim of this work was to isolate oil-degrading bacteria capable to synthesize biosurfactants and to analyze their tensioactive characteristics.Samples were isolated from a stagnant stream contaminated with oil from a wastewater treatment plant, located in Moreno, Buenos Aires, Argentina (34º 34? 50.9?? S, 58º 49? 25.6?? W). Oil-degrading bacteria were isolated by supplementing 10 ml of sample water with 10% diesel, a micronutrient solution and different concentrations of yeast extract and incubated at 28°C and 200 rpm until turbidity development. After incubation, culture aliquots were plated on LB agar. Bacteria with different colony morphology were selected; white (W), red (R), green (G), smooth brown (SB) and mucoid brown (MB). To analyze if these five isolates were able to synthesize biosurfactants, cell free supernatants of cultures growing during 5 days on E2 medium supplemented with glucose (g), sunflower oil (so) or diesel (d) as carbon source, were used to determine surface tension reduction by the drop collapsing test and emulsification activity (EI24). In all treatments, there was a decrease in the contact angle, confirming their chemical properties as biosurfactants. SB and MB showed the highest superficial tension reduction relative to distilled water in a range of 53% to 59% depending on the carbon source while the other three remaining isolates diminished the superficial tension in a range from 20 to 50%. Regarding to the EI24, SB showed a EI24 of 65% (d), 33%(so) and 50%(g), MB values were 32%(d), 47%(so) and 45%(g) and G showed an EI24 of 47%(d), 47%(so) and 28%(g). W was unable to grow in sunflower oil as sole carbon source, but presented a EI24 of 53%(d) and 44%(g). Finally R showed negligible values in this test. To analyze the chemical nature of the produced tensioactive, a crude solvent extract from the cell-free supernatants were carried on. TLC analysis showed different retardation factors, most of them were positives for carbohydrates (Molisch reactive) and G and SB presented also spots related to amino-acidic nature (Ninhydrin staining). In conclusion, 4 of the obtained isolates seem to be promising surfactants producers that could be used in enhanced surfactant bioremediation of oil contaminated soils.