Process optimization for cultivation and oil accumulation in an oleaginous yeast Rhodosporidium toruloides A29

Biodiesel is a renewable and environment friendly energy source, which is a potential alternative to petro-diesel. In the present study, mass production of microbial lipid by the yeast strain Rhodosporidium toruloides A29 was studied for biodiesel production. Realizing the importance of microbial lipids as a potential source for biodiesel, the strain was evaluated for higher biomass production using statistical modelling approach, which resulted in a lipid yield of 0.436 g/g cell dry weight. This high lipid content was achieved using RSM optimized medium containing 2.5 g/L of yeast extract, 2.75 g/L of NaNO3, 0.5 g/L of MgSO4 and 75 g/L of glucose. The production of R. toruloides was successfully scaled up in a 30 L bioreactor. In the reactor, lipid yield increased to 0.535 g/g CDW leading to a 22-fold increase in oil content after scale up. Fatty acid characterization of the oil by GC revealed that R. toruloides A29 lipids consist of 34.59% saturated fatty acids, 46.49% monosaturated fatty acids and the rest polyunsaturated fatty acid. Transesterification of the extracted yeast oil revealed that the FAME (biodiesel) formed was similar in composition to the biodiesel produced from vegetable oil. The physico-chemical properties of the transesterified SCO were in range of the biodiesel standard specifications. Thus, this makes the microbial lipids obtained from R. toruloides A29 as potential alternative oil for sustainable production of biodiesel to meet the escalating energy demands.