Sorption-desorption response for perylene uptake by wild yeasts isolated from polluted sediments

Abstract

The industrial developments over the past few decades produced deliberately and/or accidentally released of xenobiotics to the environment, remaining these areas polluted for long periods. Bioremediation is a hard issue due to the complex mixture of the xenobiotics and to soil-sorbed contaminants that are not available for biotransformation. So microorganisms must be able to uptake the sorbed-molecules or facilitate the desorption by producing surfactants. The adsorption/desorption process was scarcely studied in fungi and sorbed-compounds fixed in diverse compartments with different desorption rates. Therefore, our aims were to isolate yeasts from polluted sediments, to evaluate the perylene bioavailability and to quantify their potential uptake. Pseudozyma rugulosa and Centrolene petrophilum grew on perylene cultures and their uptake were significant in relation to the other species. Different soils, type I, II and III, with diverse organic carbon, pH, cation exchange capacity, sand, silt and clay proportions were used. Soil type-III showed the higher perylene level in the aqueous phase and sorbed to particles, nevertheless showed the higher desorption rate. Perylene availability were in relation with the soil matrix and organic content, and the desorption coefficients were significantly related with the P. rugulosa and C. petrophilum kinetic parameters. These results were in relation to the biosurfactant production by both fungal species. Desorption parameters significantly fitted perylene uptake, with R2 = 0.97 for P. rugulosa and R2 = 0.95 for C. petrophilum. Biosurfactants and extracellular enzymes production explained the perylene degradation by both yeasts, being the results confirmed by the surface tension measurements.