Published in Scientific Bulletin. Series F. Biotechnologies, Vol. XXI
Written by Ortansa CSUTAK, Alexandra SIMON-GRUIŢĂ, Viorica CORBU, Nicoleta CONSTANTIN, Daniela POJOGA, Tatiana VASSU, Georgiana DUŢĂ-CORNESCU

Phytoremediation represents an ecological and economic alternative for remediation of polluted environments. The combination of plants and xenodegrading microorganisms is often used for the improvement of the remediation process. Yeast strains Yarrowia lipolytica CMGB32, Cryptococcus curvatus YR-P2 and Rhodotorula glutinis RG5 were tested for assimilation of petroleum and n-hexadecane and biosurfactant synthesis. Y. lipolytica CMGB32 grew well on n-hexadecane over two weeks, C. curvatus YR-P2 degraded petroleum during the first ten days, while R. glutinis RG5 was more active at the beginning of incubation period. All strains produced good rates of biosurfactants. Bean (Phaseolus vulgaris) seeds were sown in pots with sterilized soil and a mixture of the three yeast strains in the presence of petroleum and n-hexadecane (2:1 v:v) and observed for a month. Similar experiments were performed using oil polluted soil from oil wells (Ploiesti area, Romania) and a mixture of polluted soil, sand and gravel. The plants grew slowly on sterilized soil, with visible results only after three weeks. The presence of oil well polluted soil allowed seed germination during the first week due probably to complex interaction between soil native microorganisms-yeast mixture-plant-pollutant which provided the necessary nutrients. Although P. vulgaris has the ability to convert contaminants in less toxic compounds and to fix atmospheric nitrogen, the yeast mixture seems to enhance the plant growth, fully developed plants being observed after two weeks compared to control plants. Soil aeration was also a determinant factor, since seeds planted in soil mixture showed the most rapid growth during first week. The results suggest a positive influence over long period of time of the yeast mixture on plant growth in presence of oil compounds. Further work aims optimization of the novel yeast-plant system as basis for phytoremediation studies.

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