Crucial role of support and water activity on the lipase-catalyzed synthesis of structured triglycerides

The synthesis of structured triglycerides (MLM) containing medium-chain fat ty acids (e.g. caprylic acid) in the 1- and 3-positions and a long-chain fa tty acid (e.g. oleic acid, linoleic acid) in the 2-position of glycerol has been investigated. Special emphasis was given on the influence of support, organic solvent, and water activity on the lipase activity. Water adsorpti on isotherms for different lipase preparations were determined. In the inte resterification between triolein and caprylic acid, best results (up to 45% CyOCy and 46% CyOO) were found with Celite-immobilized lipases from Rhizop us sp. and Rhizomucor michei at low water activity (0.11 < a(w) < 0.33) in n-hexane. V-max/K-m-values were similar using caprylic acid or the correspo nding methyl or ethyl esters. Alternatively, a two-step reaction was invest igated, where 2-monoglycerides (2-MG) were produced with a 1,3-regiospecifi c lipase from Rhizopus delemar from pure triglycerides (triolein, trilinole in) or cottonseed oil. The 2-MG were isolated and then esterified with capr ylic acid using the same lipase immobilized on polypropylene (EP 100). In t he presence of activated molecular sieves, highly pure structured triglycer ides were formed within short reaction times (< 5 h). For instance, the str uctured triglyceride derived from cottonseed oil contained >95% caprylic ac id in the 1- and 3-positions and 80% of linoleic acid and 19% stearic acid in the 2-position of glycerol.