An efficient method for the enrichment of the arachidonic acid methyl ester from Mortierella alpina-derived crude oils

• We describe a simple separation method assisted solvents for the enrichment of arachidonic acid methyl ester.
• Three methyl esterification methods were used to process the microbial oil derived from Mortierella alpina.
• Arachidonic acid methyl ester obtained better enrichment efficiency and recovery.
• This method simplifies the existing separation methods.

An improved method was developed for enriching arachidonic acid (AA) methyl ester from microbial oil by two-step low-temperature wet fractionation. The effects of solvent, operating temperature, and solvent-to-fatty acid methyl esters (FAMEs) ratio on the enrichment of AA were investigated. The best results were achieved when n-hexane was used as solvent. With operating temperatures in the range −30 °C to −80 °C and a FAMEs-to-solvent ratio of 1:5 (v/v), the proportion of AA methyl ester isolated could be increased to 83.76 ± 2.78% with a yield of 52.89%. The total recovery of AA methyl ester would be further increased to 90.84% by recrystallization of the solid phases. The 20C, 22C saturated fatty acids were enriched by n-hexane or petroleum ether at −30 °C, with concentrations increased 7.5-fold or 7.2-fold compared with their original levels, respectively. In addition, a method that combined alkali and acid catalysis of the transmethylation was the most conducive to the preparation of polyunsaturated fatty acid methyl esters.