ABSTRACT
Aims@#Oleaginous yeasts are widely used for the production of biodiesel feedstocks because of their high lipid content. This research was aimed to conduct random mutagenesis of Rhodotorula mucilaginosa using ethyl methane sulfonate (EMS) and identify the mutants with improved lipid production. @*Methodology and results@#A total of twenty-two mutant isolates prescreened with cerulenin were produced and further characterized via M13 PCR fingerprinting to determine their polymorphism and genetic distances. Eight strains, namely M1, M2, M3, M4, M7, M10, M11 and M18, were chosen based on their genetic distances from the parental strain for biomass production. Six mutants (M1, M2, M3, M4, M7 and M18) showing the highest dry cell weights were further selected for evaluation of lipid production in a laboratory-scale bioreactor using glucose as a carbon source. Results indicated that parental strain exhibited lipid content of 1.83 g/L, while strains M1, M2, M3, M7 and M18 generated 2.37 g/L, 2.27 g/L, 2.27 g/L, 3.10 g/L and 3.83 g/L of intracellular lipid, respectively. These five mutants were identified to have significant increase in lipid production compared to the parental strain. @*Conclusion, significance and impact of study@#This study demonstrated enhanced lipid production in R. mucilaginosa by random mutagenesis. New generated strains had higher lipid productivity compared to parental strain and application of these strains in industry may reduce the overall cost of biodiesel production.
ABSTRACT
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.