The gamma-linolenic acid concentrates from borage and evening primrose oil fatty acids via lipase-catalyzed esterification

γ‐Linolenic acid (GLA, all‐ cis 6,9,12‐octadecatrienoic acid) has been enriched from fatty acids of borage ( Borago officinalis L.) seed oil to 93% from the initial concentration of 20% by lipase‐catalyzed selective esterification of the fatty acids with n ‐butanol in the presence of n ‐hexane as solvent. The immobilized fungal lipase preparation, Lipozyme, used as biocatalyst, preferentially esterified palmitic, stearic, oleic and linoleic acids and discriminated against GLA, which was thus concentrated in the unesterified fatty acids fraction. In the absence of hexane, concentrate containing about 70% GLA was obtained. When the reaction conditions, optimized for borage oil fatty acids, were applied to fatty acids of evening primrose ( Oenothera biennis L.) oil, concentrates containing 75% GLA were obtained. From both oils, GLA concentrates were prepared efficiently in short reaction times (1–3 h) at 30–60°C. The process can be applied for the production of GLA concentrates for dietetic purposes.