title: Oleaginous yeasts from Ethiopia.
abstract: Oleaginous microorganisms can produce high amounts of oil (>20 % of their biomass) under suitable cultivation conditions. In this research work 200 samples were collected from soil, plant surfaces (leaves, flowers and fruits), waste oils from traditional oil milling houses and dairy products (cheese, milk and yoghurt) in Ethiopia. Three hundred and forty yeast colonies were isolated from these samples. By applying Sudan III staining tests, 18 strains were selected as possible oleaginous yeasts. The 18 strains were identified and characterized for their lipid production as a feedstock for biodiesel production in the future. They were identified using morphological and physiological methods as well as sequencing the 3'end of the small-subunit rRNA gene, the internal transcribed spacer regions (ITS; ITS 1, ITS 2 and the intervening 5.8S rRNA gene), and the D1/D2 domain of the 26S rRNA gene. The 18 yeasts were identified as Cutaneotrichosporon curvatus (syn, Cryptococcus curvatus) (PY39), Rhodotorula kratochvilovae (syn, Rhodosporidium kratochvilovae) (SY89), Rhodotorula dairenensis (SY94) and Rhodotourula mucilaginosa (SY09, SY18, SY20, PY21, PY23, PY25, SY30, PY32, SY43, PY44, SY52, PY55, PY61, SY75 and PY86). Under nitrogen-limited cultivation conditions, R. mucilaginosa PY44 produced the highest biomass (15.10 ± 0.54 g/L), while R. mucilaginosa PY32 produced the lowest biomass (10.32 ± 0.18 g/L). The highest lipid yield of 6.87 ± 0.62 g/L and lipid content of 46.51 ± 0.70 % were attained by C. curvatus (syn, C. curvatus) PY39. On the other hand, R. mucilaginosa PY61 gave the lowest lipid yield (2.06 ± 0.52 g/L) and R. mucilaginosa SY52 gave the lowest lipid content of 16.99 ± 0.85 %. The results in this research work suggest that much more oleaginous yeasts can be isolated from Ethiopian environment. On the basis of their substantial lipid production abilities, the three oleaginous yeast strains PY39, SY89 and SY18 were selected and recommended for further optimization processes.
authors.affiliation: Microbial, Cellular and Molecular Biology Department, College of Natural Sciences, Addis Ababa University, P.O. Box: 1176, Addis Ababa, Ethiopia. tamene.milkessa@aau.edu.et.
authors.forename: Tamene Milkessa
authors.initials: TM
authors.lastname: Jiru
authors.affiliation: Microbial, Cellular and Molecular Biology Department, College of Natural Sciences, Addis Ababa University, P.O. Box: 1176, Addis Ababa, Ethiopia.
authors.forename: Dawit
authors.initials: D
authors.lastname: Abate
authors.affiliation: Department of Agricultural and Biosystems-Engineering, School of Food Technology, Nutrition and Bio-Engineering, Makerere University, P.O. Box: 7062, Kampala, Uganda.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Kiggundu
authors.affiliation: Department of Microbial, Biochemical and Food Biotechnology, College of Agricultural Sciences, University of the Free State, P.O. Box: 339, Bloemfontein, South Africa.
authors.forename: Carolina
authors.initials: C
authors.lastname: Pohl
authors.affiliation: CBS-KNAW Fungal Biodiversity Center, Uppsalalaan 8, P.O. Box: 85167, 3584 CT, Utrecht, The Netherlands.
authors.forename: Marizeth
authors.initials: M
authors.lastname: Groenewald
keywords: Biodiesel; Oleaginous yeast; Single cell oil; Yeast identification