congresos y reuniones científicas
osurfactant production for bioremediation through bioaugmentation: a native strain culture optimization.
Conferencia; 6th European Bioremediation Conference; 2015
The North-Delta region of Buenos Aires is one of the largest industrial zones in Argentina, with several companies carrying out petrochemical activities. Due to this, accidental and intentional spills have occurred during the last 50 years, generating several environmental pollution to soil and groundwater. In this framework, the goal of an in-situ bioremediation strategy using laboratory-produced biosurfactants from native microorganisms ?bioaugmentation- emerged.To this goal, 13 phenotypically different microorganisms were isolated from contaminated sites; 6 of which showed good surface activity. Among them, Ag.1.A-HC strain was selected for studying its performance on producing biosurfactants at different culture conditions, namely: temperature (21°C, 25°C and 29°C) and substrate concentration (2, 4.5 and 6 %v/v). Each combination of variables were made by duplicate in 250ml Erlenmeyer flasks, containing 45ml of a mineral salt medium (MSM) supplemented with a mixture of three commercial hydrocarbons (HC; kerosene, diesel and gasoline RON 95). Cultures were inoculated with 1ml of pre-culture with an optical density of 0.200 and kept at 120rpm for 6 days. Surface tension (ST) of the cell-free culture supernatant was measured with a force tensiometer by DuNouy ring method and used as biosurfactant production indicator. Biomass concentration was measured by cell dry weight (CDW) method: known volume samples were put in a centrifuge for 15 minutes at 13500rpm, supernatant was removed, the pellet was washed using n-hexane (to remove the hydrocarbon residue) and recentrifuged. Pellet weight was determined weighing after drying at 80°C for 24h. Initial and final pH where also measured with a bench pH-meter.Main results are shown: Fig. 1. displays the decrease of the ST and in Fig. 2 the biomass concentration obtained, both with respect to temperature and HC concentration. The maximum decrease on the ST occurred at 25°C and at a concentration of 6% of HC (from 48.44 ± 0.04mN/m to 38.29 ± 0.15mN/m). In addition, the maximum biomass concentration was obtained when the microorganism was cultured at 29°C with 6% of HC (0.49 ± 0.04g/l). It is worth noting that at each temperature, the higher the HC concentration the higher the decrease in the ST value and biomass concentration. Besides, a correlation between the increase on pH value, decrease in ST and the HC concentration was also found.In conclusion, we found that Ag.1.A can grow in a wide range of temperature, being 29°C the optimal for the case. Regarding biosurfactant production, an increment of HC concentration resulted in the decrease of the ST value. This suggests that the microorganism could be producing the tensioactive compound to increase the availability of the carbon source and if this concentration becomes higher more biosurfactant must be produced. Finally, this results show that the Ag.1.A-HC strain ?currently being molecularly characterized- isolated from a hydrocarbon contaminated site could have a potential use for industrial production of biosurfactant and bioremediation technologies.Acknowledgements: The financial support by National Technological University (Argentina) and FRD (Argentina) is greatly appreciated.