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Enzymatic synthesis of medium-chain triacylglycerols by alcoholysis and interesterification of copra oil using a crude papain lipase preparation

Caro Y., Turon F., Villeneuve P., Pina M., Graille J.. 2004. European Journal of Lipid Science and Technology, 106 (8) : p. 503-512.

DOI: 10.1002/ejlt.200400955

We have examined the possibility of producing analogs of medium-chain triglycerides (MCT) from copra oil, i.e. a triacylglycerol mixture with a high content of medium-chain fatty acid moieties (C6-C10). A two-step enzymatic process was used in which copra triacylglycerols were first split with papain lipase by alcoholysis with an alkyl alcohol and then subjected to interesterification with the alkyl esters recovered using papain lipase. Effects of temperature, water activity/content, substrate ratio, biocatalyst amount, and alcohol chain length were also investigated. On the one hand, the sn-3 stereoselectivity of the lipase in the alcoholysis of copra oil with butanol has permitted a direct enrichment of caproic, caprylic and capric moieties in the synthesized butyl esters. Thus, in the batch reactor, the reaction led to about 31% conversion of the oil after 24 h, and the content Of C6-C10 acids in the synthesized esters increased from about 16% in the starting oil to almost 42%. A similar enzymatic alcoholysis in a packed-bed column bioreactor gave 31% conversion of the oil after 120 min of reactor residence time. The reaction was also very selective because the C6-C10 fatty acyl groups represented about half of the newly formed butyl esters, whereas they accounted for only 16% of total fatty acids in the starting oil. On the other hand, the transesterification of the alkyl esters recovered (highly enriched in C6-C10 fatty acyl groups) with native copra oil directly led to an increase in the content of MCT in the oil, from 18 mol-% at the beginning of the reaction to 61 mol-% of MCT after a time period of 72 h in the batch reactor.

Mots-clés : papaine; estérase; estérification; triglycéride; huile de coco; synthèse enzymatique; triacylglycérol; alcoolyse

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