Synthesis of 2-monoacylglycerols (2-MAG) by enzymatic alcoholysis of fish oils using different reactor types

Abstract

This paper studies the synthesis of 2-monoacylglycerols (2-MAGs) by alcoholysis of cod liver oil and tuna oil, catalyzed by lipases, in stirred tank (STR) and packed bed (PBR) type reactors, operating in discontinuous and continuous modes. Firstly, several lipases were tested (DF from Rhizopus oryzae, Palatase 20000L from Mucor miehei and Novozym 435 from Candida antarctica), and although the highest 2-MAG yield was obtained with lipase DF, Novozym 435 was selected due to its greater stability. 2-MAGs were then produced with this lipase in the above-mentioned reactors. Using Novozym 435 2-MAGs can be obtained by ethanolysis of TAGs, and the major operational variable is the treatment intensity (TI, lipase amount × reaction time/oil amount). The highest 2-MAG yields (63–65%) were obtained in the STR operated in discontinuous mode. For TI of over approximately 1 g lipase × h/g oil, the 2-MAGs were degraded to glycerol. This system was scaled up to 100 times the initial volume, achieving the same yield at the same TI (1 g lipase × h/g oil). Operating in continuous mode, the 2-MAG yields obtained (53–54%) were roughly 15% less in both reactors at this TI. 2-MAGs in the final reaction mixture were separated from the ethyl esters by solvent extraction using solvents of low toxicity (ethanol and hexane); 2-MAG recovery yield (g 2-MAGs extracted/100 g of 2-MAGs in the reaction mixture) and 2-MAG purity in the target product (g 2-MAGs/100 g of total product) were approximately 90%. The fatty acid profile of the 2-MAGs produced was similar to the fatty acid profile in position 2 of the original oils. The two major n-3 polyunsaturated fatty acids (n-3 PUFAs) of 2-MAGs produced were eicosapentaenoic acid (EPA) and docosohexaenoic acid (DHA), and their combined contents were about 40% and 45% for cod liver oil and tuna oil, respectively.