Extraction of Lipids from Fermentation Biomass Using Near-critical Dimethylether

The extraction of lipids from both wet and dry biomass produced by fermentation has been carried out using near-critical dimethylether (DME) as the extraction solvent. Fermentations were carried out from a shake flask to 300 litre scale using the micro-organism Mortierella alpina, and up to a 20 litre scale for Phaffia rhodozyma and Agrobacterium tumefaciens. The lipids extracted at a laboratory and pilot scale from the biomasses were enriched in arachidonic acid, astaxanthin, and co-enzyme Q10 respectively. Extractions were also performed on marine microalgae, produced by fermentation elsewhere, to obtain lipids rich in EPA. Lipids could be extracted from wet biomass using DME, which could result in improved process economics. However, water is co-extracted, which has to be separated from the lipid. The biomass shrunk considerably during packed bed extraction, leading to channelling. In contrast, the extraction of lipids from freezedried biomass was routine, and yields were substantially higher than using CO2 or CO2 + ethanol. DME also extracted polar lipids from both wet and dry biomass, leading to the higher yields. Further work was also performed on fractionation and/or chemical modification of the lipids that were extracted by DME.