Preparation of Triacylglycerols Enriched in DHA from Single Cell Glycerides via Molecular Distillation and Enzymatic Glycerolysis

In the present study, the total lipids from Schizochytrium sp. were ethylated, and ethyl esters (EE) enriched in docosahexaenoic acid (DHA; C22:6n-3) were obtained through molecular distillation and converted to glyceride form via lipase-catalyzed glycerolysis under vacuum with activated clay as absorbents in a nonsolvent system. Total lipids were extracted from dry powder of Schizochytrium sp., which was followed by lipase catalyzed ethylation. EE with 83.04% DHA was obtained through a three-stage procedure of molecular distillation. The effect of vacuum, temperature, reaction time, substrate ratio, and enzyme dosage on glycerolysis was investigated. Vacuum and increase in temperature had a positive effect on glycerolysis, and the increase in substrate ratio led to an increase in triacylglycerol (TAG) content but a decrease in EE conversion. The adsorption of glycerol onto activated clay played a positive role in glycerolysis, and the operational stability of immobilized lipase. The conditions which gave the glycerides with more than 75% TAG were 60 degrees C, 24 h, 0.048 mol EE, 0.016 mol glycerol, 2.25 g activated clay, and 3% Lipozyme 435, and the immobilized lipase showed good operational stability in 10 batches of reactions with activated clay as absorbent.