Lipase‐Catalyzed Butanolysis of Echium Oil for the Selective Enrichment in Gamma‐Linolenic and Stearidonic Acids

Abstract

Enzymatic butanolysis of Echium oil in the presence of lipases from Candida rugosa and Rhizopus oryzae has been studied. The effects of lipase immobilization, hydration of the reaction mixture and oil oxidation degree on lipase catalytic activity, fatty acid selectivity, and inactivation degree are evaluated. The utilization of butanol containing 2.5% (w/w) of water produces the highest catalytic activity of lipases in both powder and immobilized form; particularly of immobilized lipase from Rhizopus oryzae, which led to the complete conversion of triacylglycerols. The presence of 2.5% water also improves the biocatalyst stability, as the rate of immobilized lipase from Rhizopus oryzae inactivation (Kd = 0.0084 h−1) is much lower than in the absence of water (Kd = 0.0285 h−1). Stability of immobilized lipase from Rhizopus oryzae further increases when bleached oil is used (Kd = 0.0008 h−1). Then, fatty acid selectivity of immobilized lipase from Rhizopus oryzae is investigated by determining competitive factors for each fatty acid from Echium oil. Results indicates a very good activity, stability, and very important discrimination of this lipase against stearidonic and gamma‐linolenic acids which can be utilized for the efficient and selective oil enrichment in polyunsaturated fatty acids.Practical Applications: This study describes an interesting methodology for the selective enrichment in polyunsaturated fatty acid from Echium oil utilizing intact triacylglycerols as starting material. This study also evaluates the lipase inactivation as a crucial tool for industrial application of this bioprocess. Finally the study describes the production of lower glycerides that can be used as precursors of structured bioactive lipids enriched in stearidonic and gamma‐linoleic acids.Schematic representation of the simultaneous reactions that occur in the butanolysis reaction carried out. SAFA saturated fatty acid, MUFA monounsaturated fatty acid, PUFA polyunsaturated fatty acid, FABE fatty acid butyl ester, BUTOH Butanol.