Sorbed Anthracene Degradation by Sophorolipid Producing Yeasts

The organic pollutan adsorption/desorption process by microbial degradation had been less studied than metal ones. The sorption assays alone did not predict desorption, due to hysteresis, irreversibility, fixed compounds in different sites, with diverse desorption rates. Most of the studies dealt with bacteria rather than filamentous fungi and yeasts. So, our aims were to isolate yeasts from polluted sediments, to quantify its potential to uptake anthracene (An) and to evaluate the bioavailability by a desorption model. Yeasts were isolated from hydrocarbon-polluted samples, 40-isolates grew in anthracene-plates. Molecular characterization was achieved by sequence analysis of the ITS1-5.8S rRNA-ITS4 and 26S rRNA regions; morphological and physiological determination were also done. Candida parasilopsis, Pichia anomala and Rhodothorula mucilaginosa were the prevalent yeasts. An-degradation was assessed in soil-systems with 0, 50, 100, 150, 200 and 250 µg An/l, 3 differentes sorbens types, organic carbon, organic nitrogen, PAHs, sand:silt:clay, pH and cation exchange capacity. Sophorolipids excretion were confirmed by HPLC, UV-detector with active fraction at 9.669 min (RT 9.646 min = sophorolipid-standard). A desorption model with equilibrium, nonequilibrium and nondesorption areas, was applied to explain the experimental data, An-transformation was greater in the organic liquid-phase than in the soil-sorbed ones; the desorption-coefficients and soil components were negatively correlated with the kinetic parameters. The An-release depended on the sophorolipid excretion, soil matrix and particles sizes. Desorption parameters significantly fitted the yeast uptake, with R2 = 0.97, R2 = 0.90 and R2 = 0.97 for C. parasilopsis, P. anomala and R. mucilaginosa, respectively

Power rheology model tto assess bacteria growth in activated sludge polluted with phenanthrene

Environmental biotechnology is a scientific and engineering system that use microorganisms to detoxificate solid, liquid and gaseous wastes. Activated sludge is a biotechnology that clean up sewage and industrial wastewaters using air and biological flocs. Different mathematical models expressed the bacteria growth in relation to the sludge parameters. The Power model described the relationship between the shear rates of the sludges with hydrocarbon and Leptothrix spp. flocs sizes; and was expressed as: Ƭ = K . ɣ n. Where: (Ƭ) was the shear stress, (K) indicated the sludge viscosity, (ɣ) was the shear rates and was the flow behavior index. The assays were performed to evaluate the thick wooly flocs formation with and without phenanthrene. At low inoculum sizes (105 cells/m3), most of the flocs were larger than 3 µm, and the cellular yield was 0.3-0.6 mg dry wt/ml. In contrast, with higher inoculums (109 cells/m3), flocs of 2 µm were observed, and the bacterial yield was around a constant value c.a. 1.6 g dry wt/m. The relation of the inoculum with the flocs sizes responded to an hyperbolic curve. This phenomenon was related to poor growth due to oxygen limitation and hydrocarbon presence inside the large flocs. The experimental data were tested by the Power model, and the R2 obtained indicated the goodness of the fit to the bioassays. The optimization of bioremediation strategies like the bacterial bioaugmentation in activated sludge, confirmed that the Power model provided the best prediction of viscosity that determined the aeration with the suspended solids and phenanthrene present in the sludges.Fil: Romero, Maria Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Chiaravalli, Juan C.. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; ArgentinaFil: Urrutia, María Inés. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales; ArgentinaFil: Moreno Kiernan, Alejandro Ricardo. Provincia de Buenos Aires. Ministerio de Salud; Argentin