Effects of lipids on n-alkane attenuation in media supporting oil-utilizing microorganisms from the oily Arabian Gulf coasts

Abstract

The Arabian Gulf is one of the most extensively oil-polluted areas of the world. The major objectives of this work were to study whether hydrocarbon-utilizing microorganisms indigenous to that area would readily accumulate added lipids, and whether this might affect their hydrocarbon consumption potential. Two prokaryotes, Arthrobacter nicotianae KCC B35 and the unidentified organisms KCC B6, as well as one eukaryote, Candida parapsilosis KCC Y1, were selected for this study. Biomass samples of the test organisms were incubated in an inorganic medium containing various concentrations of cholesterol, stearic acid, triolein or egg-phospholipids. The results revealed that all lipid classes were readily accumulated by the three test organisms. In addition, biomass samples were incubated for 6 h in an inorganic medium containing mixtures of individual lipid classes and either n-octadecane or n-docosane. The cells were removed and the residual alkanes in the medium were quantitatively recovered and analyzed by GLC. The results showed that out of the tested lipid classes only stearic acid exhibited a common stimulatory effect on the consumption of both n-alkanes by all test organisms. Other lipid classes were either inhibitory or had less pronounced effects than stearic acid. ß

Candida digboiensis sp. nov., a novel anamorphic yeast species from an acidic tar sludge-contaminated oilfield

“…As C. digboiensis strains were isolated from an acid tar sludgecontaminated soil, we have investigated which other species have been isolated from hydrocarbon habitats. Although very few reports are available on the isolation of yeast species from oil-contaminated soil, yeast strains have been isolated from oilfields and oil brines in Japan (Iizuka & Goto, 1965;Iizuka & Komagata, 1965), and some yeast species have been reported to utilize petroleum hydrocarbons (Ismailov, 1985a, b;Palittapongarnpim et al, 1998;Radwan et al, 2001). We have examined the habitats of the closest relatives of C. digboiensis.…”