Bioconversion of crude glycerol to microbial lipid using a robust oleaginous yeast Rhodosporidium toruloides ATCC 10788 capable of growing in the presence of impurities

Abstract

In this work, crude glycerol, a by-product from a biodiesel industry was characterized and converted to microbial lipid. The sample of crude glycerol was found to contain 44.56wt.% glycerol, 13.86wt.% methanol, 10.74wt.% of ash and 32.97wt.% of soap. Rhodosporidium toruloides ATCC 10788 was studied for the first time to determine its ability to grow on crude glycerol as a carbon source. Methanol concentration as low as 0.5% (w/v) in the medium containing pure glycerol inhibited biomass and lipid production by this strain. However, higher concentration of methanol (i.e. 1.5% w/v) in crude glycerol containing media did not have the same effect on the organism, with double the biomass (21.16g/L), triple the lipid concentration (11.27g/L) and high lipid content (53.28wt.%) produced at the end of 168h. Unlike many other oleaginous microorganisms, the ability of this yeast to consume other impurities present in crude glycerol enhanced the growth and lipid production in such a way that the effect of methanol was masked or became insignificant. The lipid obtained contained 47.16% of oleic acid (a monounsaturated fatty acid), making it a very good feedstock for some oleochemical industries and the production of biodiesel. This bioconversion process which involves the production of lipid from crude glycerol waste stream will be of great interest to the biodiesel industry as it can be easily integrated into the existing biodiesel production plant. The use of such robust strains to produce other value added products can also be explored.