Abstract
Rhodotorula kratochvilovae (syn, Rhodosporidium kratochvilovae) SY89, an oleaginous yeast, isolated from Ethiopian soil, was grown under nitrogen-limited media. The capacity this with respect to biomass production, lipid yield and lipid content was evaluated. The influence of inoculum size, carbon sources, variations in glucose concentration, nitrogen sources, C/N ratio, pH, temperature, agitation, and aeration rate and incubation period were investigated. Inoculum size of 10% v/v, glucose as a carbon source at 50 g/L glucose, 0.50 g/L yeast extract and 0.31 g/L (NH4)2SO4, C/N ratio of 120, pH 5.5, incubation temperature of 30 °C, 225 rpm, 0.2 as aeration ratio and 144 h of incubation were found to be optimum conditions for lipid production. Then the yeast was grown in a batch bioreactor by combining the different optimized parameters together. Under the optimized conditions, the yeast gave maximum biomass (15.34 ± 1.47 g/L), lipid yield (8.60 ± 0.81 g/L) and lipid content (56.06 ± 1.70%). The dominant fatty acids exhibited in order of their relative abundance (%w/w), were oleic, palmitic, linoleic, stearic, linolenic and palmitoleic acids. The concentration of saturated and monounsaturated fatty acids adds up 78.63 ± 2.19%. This suggests that this strain could be used as a good feedstock for biodiesel production.
Highlights
Microorganisms that are capable of accumulating lipids above 20 up to 70% of their dry biomass are termed as oleaginous (Ratledge and Wynn 2002)
Rhodosporidium has been transferred to Rhodotorula and the oleaginous yeast Rhodosporidium kratochvilovae is renamed as Rhodotorula kratochvilovae (Wang et al 2015)
After screening using Sudan III stain and determination of oil content of 340 yeast strains isolated from the soil, plant surfaces, dairy products and wastes from traditional oil milling houses, it was found that the yeast strain SY89, which was isolated from soil contained high oil content (39.33 ± 0.57% w/w)
Summary
Microorganisms that are capable of accumulating lipids above 20 up to 70% of their dry biomass are termed as oleaginous (Ratledge and Wynn 2002). The production of microbial oil has many advantages which include: high growth rate, short life cycle, less labor requirement, less affection by venue, season and climate, no arable land needed, easier to scale up (Li et al 2008), and ability to use different carbon sources (Economou et al 2011). Many basidiomycetous yeasts including Rhodosporidium are included in other existing or new genera (Wang et al 2015). Rhodosporidium has been transferred to Rhodotorula and the oleaginous yeast Rhodosporidium kratochvilovae is renamed as Rhodotorula kratochvilovae (Wang et al 2015)
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