Extraction of lipids from Yarrowia lipolytica
Résumé
BACKGROUND: Microorganisms have often been considered for the production of oils and fats as an alternative to agricultural and animal resources. Extraction experiments were performed using a strain of the yeast Yarrowia lipolytica (Y. lipolytica), a high-lipid-content yeast. Three different methods were tested: Soxhlet extraction, accelerated solvent extraction (ASE) and supercritical carbon dioxide (SCCO₂) extraction using ethanol as a cosolvent. Also, high pressure solubility measurements in the systems "CO₂ + yeast oil" and "CO₂ + ethanol + yeast oil" were carried out. RESULTS: The solubility experiments determined that, at the conditions of the supercritical extractor (40°C and 20 MPa), a maximum concentration of 10 mg of yeast oil per g of solvent can be expected in pure CO₂. 10% w/w of ethanol in the solvent mixture increased this value to almost 15mg of yeast oil per g of solvent. Different pretreatments were necessary to obtain satisfactory yields in the extraction experiments. The Soxhlet and the ASEmethod were not able to complete the lipid extraction. The "SCCO₂ + ethanol" extraction curves revealed the influence of the different pretreatments on the extraction mechanism. CONCLUSION: Evaluating the effectiveness of a given pretreatment, ASE reduced the amount of material and solvent used compared with Soxhlet. In all three cases, the best total extraction performance was obtained for the ethanol-macerated yeast (EtM). Addition of ethanol to the solvent mixture enhanced the oil solubility. Oil can be extracted from Y. lipolytica in two different steps: a non-selective ethanol extraction followed by TAG-selective SCCO₂ purification.
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