Optimization of lipid production by locally isolated Rhodotorula toruloides using response surface methodology

Biodiesel has received increasing interest as green and sustainable fuel replacing the depleting fossil-based diesel. Oleaginous yeast has been known able to produce lipids as biodiesel feedstock during nutrient limitation. Recently, an oleaginous yeast identified as Rhodotorula toruloides was successfully isolated from a highly acidic runoff water sample. This study was conducted to evaluate and optimize the lipid production of the Rhodotorula toruloides using response surface methodology. Sudan test was conducted to evaluate the lipid production by the yeast qualitatively. A central composite experimental design was adopted to optimize pH, temperature and C/N ratio for lipid production. The interaction of the process variables was studied. The Sudan test demonstrated colour changes that occurred on media containing yeast, indicating its ability to produce lipids at all tested parameters. Statistical data analysis showed a high coefficient of determination (R2) determined at 0.9183 with a predicted optimum lipid yield of 5.6% produced at pH 5.6, 27.7°C and a C/N ratio of 107.29. The optimized conditions for the yeast were further tested and the resulting observed lipid yield was 7.7%. The finding of this study provides insightful knowledge for the large-scale production of microbial oil using oleaginous yeast.