Lipase‐catalyzed hydrolysis of TG containing acetylenic FA

Hydrolysis of symmetrical acetylenic TG of type AAA [viz., glycerol tri‐(4‐decynoate), glycerol tri‐(6‐octadecynoate), glycerol tri‐(9‐octadecynoate), glycerol tri‐(10‐undecynoate), and glycerol tri‐(13‐docosynoate)] in the presence of eight microbial lipases was studied. Novozyme 435 (Candida antarctica), an efficient enzyme for esterification, showed a significant resistance in the hydrolysis of glycerol tri‐(9‐octadecynoate) and glycerol tri‐(13‐docosynoate). Hydrolysis of acetylenic TG with Lipolase 100T (Humicola lanuginosa) was rapidly accomplished. Lipase PS‐D (Pseudomonas cepacia) showed a fair resistance toward the hydrolysis of glycerol tri‐(6‐octadecynoate) only, which reflected its ability to recognize the Δ6 positional isomer of 18∶1. Lipase CCL (Candida cylindracea, syn. C. rugosa) and AY‐30 (C. rugosa) were able to catalyze the release of 10‐undecynoic acid and 9‐octadecynoic acid from the corresponding TG, but less readily the 13‐docosynoic acid in the case of glycerol tri‐(13‐docosynoate). The two lipases CCL and AY‐30 were able to distinguish the small difference in structure of fatty acyl moieties in the TG substrate. To confirm this trend, three regioisomers of mixed acetylenic TG of type ABC (containing one each of Δ6, Δ9, and Δ13 acetylenic FA in various positions) were prepared and hydrolyzed with CCL and AY‐40. The results reconfirmed the observation that AY‐30 and CCL were able to distinguish the slight differences in the molecular structure (position of the acetylenic bond and chain length) of the acyl groups in the TG during the hydrolysis of such TG substrates.