Factors Affecting Microbial Oil Accumulation by Oleaginous Yeast

The growth performance and intracellular lipid production potentiality of two identified yeast stains Candida tropicalis (S5) and Issatchenkia orientalis (D5) in N-limited medium under different carbon, nitrogen sources, carbon/nitrogen ratio and temperature was studied. Among all carbon sources, glucose was the best in lipid weight, lipid content, lipid yield and lipid productivity. The increases in cell biomass reached its maximum value by use of yeast extract in Candida (8.62 gL-1) and 10.25 gL-1 for Issatchenkia using peptone. However, urea was the preferable N source for lipid production in both strains. On the other hand, KNO3 proved to be the lowest values treatment in the cell biomass and lipid production for both strains. The interaction treatments yeast extract + (NH4) SO4 was convenient for oil yield parameters in Candida. The data showed that the maximum cell biomass was obtained at 54 and 100 C/N ratio for Candida and Issatchenkia, respectively. The data also exhibited that designated sharp increases in lipid weight, lipid content and lipid productivity were developed by the two yeast strains reached their maximum values at C/N ratio 115 (1.0 gL-1, 27.77%, 0.20 gL-1) for Candida tropicalis and C/N ratio 100 (3.37 gL-1, 30.92%, 0.67 gL-1) for Issatchenkia orientalis. Further increase in C/N ratio resulted in drop in lipid weight; this drop was slight in Candida above 115, whereas it was drastically in Issatchenkia after C/N 100. The result of effect of temperature degree on cell biomass and lipid production showed that the temperature degree of 30°C was the best for yeast growth and also for lipid production.