Biosurfactant production and characterization from Antarctic bacteria for enhancing bioremediation of hydrocarbon-contaminated soils

ROSSI A; MARTINEZ ALVAREZ L; RUBERTO L; MAC CORMACK W.P

Mendoza

Encuentro; LVIII reunión anual de la SAIB; 2022

SAIB

Introduction. Hydrocarbon contamination is a global problem, also affecting Antarctica. Bioremediation, particularly biostimulation, is an adequate tool for the recovery of contaminated soils. Nonetheless, a certain portion of the contaminants are recalcitrant and other strategies are required. Biosurfactant-producing strains provide the advantage of increasing the bioavailability of hydrophobic substrates such as total petroleum hydrocarbons (TPH) through the production of amphiphilic molecules -i.e., surfactants. Objective. To identify suitable Antarctic microorganisms for biosurfactant production. Characterization and quantification of the produced surfactant activity. Methods. 28 microbial strains were isolated from hydrocarbon-contaminated soils near Carlini Station (Antarctica, Argentina) and identified up to Genera using the 16S (bacteria) or 18S (for fungi) RNA genes. CTAB/Methylene Blue agar plates were used as a screening method for biosurfactant production. Growth kinetics were followed by optical density determinations at 600nm. Surfactant activity was assayed by emulsification index 24 hrs. (EI24), hemolytic assay, drop collapse test, and oil displacement test. Results. 3 out of the 28 strains resulted positive for surfactant production in the CTAB/MB plates. 2 of those strains belonged to Pseudomonas (strains 9 and 14), while the remaining one belonged to the Rhodococcus genus (named ADH). Emulsification indexes (24) up to 58% (Pseudomonas) and 63% (Rhodococcus) were determined at cultivations days 5 and 7, respectively. Stationary phases were achieved after 24 and 48 hrs, respectively. The three strains resulted in hemolytic when assayed on blood agar plates. In the drop collapse test and oil displacement, strains 9 and 14 resulted in positive. Conclusion. Three strains (two Pseudomonas sp. and one Rhodococcus sp.) were isolated and identified as promising biosurfactant producers with potential application in bioremediation and MEOR (Microbiological enhanced oil recovery)