Sunday, April 29, 2007

Biosurfactant production by bacterium strain isolated from petroleum contaminated soil

Marcio A. Zago, Anderson Phillipy, Cleide M. F. Soares, Sara Cuadros Orellana, and Alvaro S. Lima. Instituto de Tecnologia e Pesquisa, Universidade Tiradentes, Av. Murilo Dantas, 300, Farolandia, Aracaju - SE, 49032-490, Brazil

Many isolated microorganisms from soils are able to produce an anphifilic substance called biosurfactant, which has as advantages its biodegradability, low toxicity and ecological acceptability. Amongst infinity of biosurfactant applications include bioremediation, food and pharmaceutical process. Petroleum is a common environmental pollutant, causing many problems with soil and groundwater contamination. This work had as objective to evaluate the carbon source, optimum time of inductor addition (petroleum), pH value, agitation speed and temperature in the biosurfactant production. Five bacteria strains were isolated from petroleum contaminated soil and codified as Biopetro 1 to 5. All these strains are Gram-negative.  The fermentations were carried out in 500 mL Erlenmeyer flaks containing 200 mL of medium prepared with different carbon source (glucose, sucrose, fructose, molasses and starch), petroleum as an inductor and 24 h age inoculum. Different pH values (4.0-7.0), agitation speeds (0, 100 and 200 rpm) and temperatures (26 - 34oC) were tested. The process was monitored by analyzing the biomass concentration, pH value and emulsification activity (EA). Starch and molasses were found to be the best carbon sources, given emulsification activities of 1.33 and 0.74 U, respectively. It was also observed that the highest agitation speed (200rpm) and intermediate temperatures in the range of 28 to 31oC were the best conditions to increase the EA. The highest EA occurred at the end of the fermentation, 168h after the inductor addition.