Single Cell Oil Production from Petroleum Sludge by Native Yeast Strains

In this research, 11 yeast strains with ability to grow on petroleum sludge were isolated from effluent of a petroleum refinery. Based on growth on mineral media contaminated petroleum sludge, two isolates were selected as the super strains. Meanwhile, results based on biochemical and morphological experiments on the strains indicated that the two selected isolates belonged to Candida and Prototheca genus. Optimization with Taguchi Statistical Method (TSM) indicated that appropriate conditions for both isolates considering sludge concentrations, nitrogen source, pH, temperature and shaking rate (rpm) are equal to 10%, 2 g/l sodium nitrate, 6.5, 25°C and 190 rpm, respectively. Biomass production in optimal growing conditions for Candida and Prototheca were 1.54 g/l and 2.3 g/l, respectively. Gas Chromatography analyses of extracted fatty acids from supernatants and surface portions after methyl-esterifies with methanol: KOH solvents, indicated that content quantity of fatty acids on the surface was more than other portions and mainly in the forms of 16 and 18 saturated carbons and in the forms of palmitic acid and stearic acid. Therefore, these isolates can be used for recycling of petroleum sludge in production of yeast biomass and cell oil.