TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Method: In obtaining biodiesel, the biomass obtained in (a) is subjected to a separation of the triglycerides contained in it as a precursor to their subsequent conversion into a mixture of fatty acid esters according to (b). The separation is an extraction. The triglyceride content in the biomass is 20-70% dry weight. The microorganism is a yeast of the genus Rhodosporidium, preferably Rhodosporidium toruloides CECT 13006 or CECT 13007. The glycerine is 70-100% of the carbon source. The method further comprises addition of vegetable seed oil to biomass obtained in (a) as a prelude to their conversion into fatty acid esters. Step (b) is performed by alcoholysis carried out in acid medium. The alcoholysis is conducted at 40-70 degrees C, preferably 50-70 degrees C. The alcoholysis is carried out with methanol or ethanol, preferably methanol. Alternatively, obtaining biodiesel comprises: (a) obtaining a microbial biomass with a triglyceride content less than 20% by dry weight, using an oleaginous microorganism using glycerine as a carbon source; (b) optionally separation of triglycerides of microbial biomass; (c) conversion of the triglycerides contained in the biomass obtained in (a) or triglycerides separated in (b) in a mixture of fatty acid esters by alcoholysis in an acidic medium, to obtain a phase comprising esters fatty acids and other phase comprising glycerine and cellular debris; (d) a first phase separation comprising esters of fatty acids and glycerol comprising phase and cell debris from (c); (e) neutralization of the phase comprises the esters of fatty acids separated in (d) to obtain a phase comprising fatty acid esters and a phase comprising water and traces of alcohol; (f) a second phase separation comprising fatty acid esters and phase comprising water and traces of alcohol from (e); (g) purification of phase comprising fatty acid ester separated in (f) obtaining a microbial biomass with a triglyceride content less than 20% in dry weight, using an oleaginous microorganism using glycerine as a carbon source. In selecting oleaginous microorganisms capable of accumulating triglycerides using glycerol as carbon source, in (i), the culture medium comprises maltose methyl green (MMG) medium. Step (ii) includes a sampling staining and analysis by fluorescence. Preferred Microorganism: The oleaginous microorganisms are able to accumulate triglycerides containing less than 20% by dry weight. EXAMPLE - No suitable example given.