Oleaginous yeasts from Brazilian Cerrado for sustainable biodiesel production using crude glycerol

The global oversupply of crude glycerol, a byproduct of biodiesel production, needs innovative strategies for its sustainable utilization. In this study we isolated and characterized oleaginous yeast strains from fruit surfaces in the Brazilian Cerrado biome, a biodiversity hotspot, to assess their potential for converting crude glycerol into microbial lipids suitable for biodiesel. From 150 fruits, 45 yeast strains were isolated, with six identified as oleaginous (intracellular lipids > 20% dry biomass). Molecular identification via ITS and D1/D2 sequencing analysis revealed affiliations with Rhodotorula toruloides and Pseudozyma species (P. hubeiensis, P. flocculosa, P. rugulosa). Lipid profiling showed predominant fatty acids (palmitic, oleic) aligning with biodiesel standards. Biodiesel properties derived from yeast lipids, including cetane number (58-62), viscosity (3.8-4.2 mm²/s), and density (864-902 kg/m³), complied with ASTM D6751 and EN14214 specifications, except for slightly elevated density in one strain. Rhodamine B screening demonstrated higher specificity for oleaginous yeasts compared to Nile Red. Phylogenetic analysis confirmed evolutionary relationships among isolates and type strains. These findings highlight the Cerrado's microbial diversity as a reservoir for robust oleaginous yeasts, offering a dual solution for crude glycerol valorization and sustainable biodiesel production. The study underscores the potential of Pseudozyma spp. and R. toruloides for integrated biorefineries, combining lipid production with biosurfactant and enzyme synthesis to enhance economic viability.