Reactivity of medium-chain substrates in the interesterification of tripalmitin catalyzed by papaya lipase

Reactivity of different medium-chain substrates, i.e., n-octanol, caprylic acid, and its alkyl (methyl, ethyl, n-propyl, and n-butyl) esters, was assessed in the interesterification of tripalmitin catalyzed by papaya (Carica papaya) lipase. Alcoholysis with n-octanol was the fastest reaction leading to the highest conversion of tripalmitin to n-octyl palmitate and concomitant formation of di- as well as monopalmitoylglycerols. This was followed by transesterification of tripalmitin with n-butyl and n-propyl caprylates, which in turn were faster than transesterification with ethyl and methyl caprylates, yielding in each case the corresponding alkyl palmitates and triacylglycerols containing palmitoyl and capryloyl moieties as the major reaction products. Acidolysis of tripalmitin with caprylic acid yielded palmitic acid and triacylglycerols containing palmitoyl and capryloyl moieties as the major reaction products, however, with the lowest conversion among the three interesterification reactions studied. In each case, interesterification was accompanied by some hydrolysis of tripalmitin.