Biomass production optimization of an efficient atrazine degrading consortium isolated from Argentinean Humid Pampa

CALABRÓ LÓPEZ, A.; BUSTO V.D.; RODRIGUEZ TALOU, J.; GIULIETTI, A.M.; CUADRADO, V.

Barcelona, Spain

Congreso; 14th EUROPEAN CONGRESS ON BIOTECHNOLOGY. Symbiosis.; 2009

Bioremediation is a well known tool used to degrade or transform contaminants to non or less toxic products, reducing the environmental pollution. Bioaugmentation is the strategy commonly employed to provide specific degrading microorganisms in sufficient numbers in order to improve biodegradation. The Argentinean Humid Pampa (AHP) region represents one of the prime agricultural lands in South America. These humic-matter-enriched soils are under intensive agricultural practices, with annual crop rotations and the irreplaceable use of agrochemicals, being atrazine among the most frequently employed. Since its half life in soil is up to 120 days and billons of tons are applied every year, the natural degradation capacity of the soil is often exceeded and herbicide residues remain as environmental pollutants. Isolation of microorganisms with atrazine degrading capabilities was carried out from soils of the AHP. A four bacterial members consortium resulted to be the more effective in atrazine removal. To conduct an efficient bioremediation process it is necessary to achieve an inoculum with high biomass and efficient atrazine degradation activity. In this way physicochemical variables such as inoculum size, stirring speed, media pH and different citrate and glucose concentrations (1,0; 2,0; 6,0 and 10,0 g/l) were studied. Shaked flask experiments were carried out in 250 ml erlenmeyers containing 50 ml of a defined media with atrazine (200 ppm) as sole nitrogen source. Biomass, atrazine removal and carbon source consumption were monitored over time. A higher biomass production was observed at 10% inoculum size and at a stirring speed of 200 RPM. However, the specific growth rate was higher at 300 RPM. With glucose as carbon source the cell yield was one fold higher and the lag phase was shorter (24 hs) than with citrate (96 hs). The atrazine degradation began after 24 hs and a complete dissipation was observed at 144 hs of culture with both citrate concentrations (1,0 and 2,0 g/l). No atrazine consumption was observed at higher citrate concentrations while the use of glucose did not show repression of the catabolic activity under 10g/l. Results show that glucose is a good option to obtain consortium biomass with high atrazine degradation activity. However, further studies are being performed to find a commercial available and low cost nutrient source which could be use, like glucose, as carbon and energy source.