Hetero-azeotropic distillation: Combining fungal dehydration and lipid extraction

A low-cost single-stage laboratory process combining fungal dehydration and lipid extraction was compared with a traditional two-stage method employin g freeze-drying and subsequent mechanical disruption in the presence of sol vent. The ability of a number of organic solvents to form hetero-azeotropes with water was exploited. Chloroform, cyclohexane and hexane were assessed in their abilities to both dry and extract lipid from the oleaginous phyco mycete Mortierella alpina (ATCC 32222). Drying rate and Lipid extraction we re maximised under conditions that prevented fungal agglomeration. The tota l processing time was limited by the rate of dehydration rather than by the rate of lipid extraction. In all cases azeotropic distillation facilitated a greater rate of dehydration than was possible with freeze-drying. A cons equent reduction in overall processing time was observed. Uniquely, both th e solvent used and the mode of mixing employed controlled the morphology of the aggregates formed during distillation. In combination with mild mixing chloroform discouraged agglomeration whereas cyclohexane and hexane promot ed aggregation. Successful lipid extraction was dependent on the use of dry biomass rather than on the application of heat to effect distillation. Nei ther the application of heat nor the solvent employed had any significant e ffect on the lipid composition of the extracted oil.