Strategies for an improved extraction and separation of lipids and carotenoids from oleaginous yeast

Currently, downstream processing of oleaginous yeast is expensive and unfeasible. To decrease processing costs and support the industrial application of this type of microorganism, this study proposes a new strategy for simultaneous recovery and further separation of lipids and carotenoids from oleaginous yeast. Assays were performed using the strain Rhodosporidium toruloides NRRL Y-1091. Characterization of this yeast revealed contents of lipids and carotenoids of 20.6 ± 1.1% and around 1.0%, respectively. γ-carotene was the main carotenoid produced by the yeast. Saponification of yeast cells with alcoholic KOH and further extraction with hexane was the most appropriate method to extract and separate lipids and carotenoids. This method applied on yeast cells disrupted by bead milling allowed to recover 75.0 ± 2.2% lipids (with a selectivity of 99.9 ± 0.0%) and 70.6 ± 3.0% carotenoids (selectivity of 98.1 ± 0.1%). Additionally, 14.9 ± 0.6% proteins were also recovered. When saponification with alcoholic KOH was conducted on whole wet cells, 85.9 ± 3.9% of lipids (selectivity of 99.9 ± 0.0%) and 78.7 ± 2.4% carotenoids (selectivity of 81.5 ± 0.5%) were recovered, and no proteins. Purity of the recovered lipids was the same using whole or disrupted cells, but the purity of the carotenoids recovered was significantly higher when the process was applied on disrupted cells. Finally, the process reported in this study allowed to extract lipids and carotenoids from oleaginous yeast with high efficiency and purity, and extra recovery of proteins.