Optimization of Diauxienne Growth of Pseudomonas aeruginosa in the Bioremediation of Soils Polluted by Hydrocarbons
Bassirou Mahamadou Harouna and Othmane Benkortbi
Journal Title:Acta Scientific Microbiology
The objective assigned to this study is the optimization of azote nutriment source for the microbial bioremediation to contribute to the fight against environmental pollution through the production of biosurfactants of multidisciplinary interest. This study consists of metabolizing hydrocarbons into biosurfactants using Pseudomonas aeruginosa ATCC 27853 strain in order to control the environmental threat in a batch of 250 ml at 37°C for 48 hours of culture. The optimization tests of nitrogen source showed that within a range of concentration [1 - 8] g/l, the optimum value was 4 g/l for KNO3 with an emulsification index EI24 = 71.45% and an optical density DOX = 0.55 for 46h of culture. The yields obtained Yx/s and Yp/s were of 60.00% and 32.17% respectively with an amount of biosurfactants P = 580 mg, a bioconversion rate θ = 78.47% and a ratio N/C = 0.473. The comparative study between two nitrogen sources such as KNO3 and NH4NO3 for a range of concentration [3 - 4] g/l demonstrated that the best source of nitrogen remains KNO3. Indeed, the kinetic monitoring of the biomass growth, the emulsification index, the biosurfactants productivity and the consumption of the substrate revealed the inhibition of the strain by NH4NO3 after 7 hours of incubation, provoking the degeneration of the strain and slowing the removal of pollutants process. A similar study of NH4NO3 at a concentration of 4 g/l resulted in an emulsification index EI24 = 65.22%, a yields Yx/s = 18.37% and Yp/s = 45.17% and a bioconversion rate θ = 57.36%. The amount of the biosurfactants measured at P = 590 mg for an N/C ratio of 0.739. In fact, the results of this study demonstrated that KNO3 promotes the growth of biomass as well as the production of biosurfactants who play a major role in the enrichment of the soil by solubilizing the toxic elements and maximum removal of hydrocarbons following diauxic phenomena.