Germinating Rapeseed as Biocatalyst: Hydrolysis of Exogenous and Endogenous Triacylglycerols

Germinating oilseeds are well-known sources of lipases (triacylglycerol acylhydrolases, EC 3.1.1.3). Seedlings of low-erucic rape (Brassica napus cv. Ceres) at day 3-5 of germination have been homogenized in Tris-HCl buffer and the homogenate used as biocatalyst for the hydrolysis of low-erucic rapeseed oil. The rape seedlings were found to be highly active in the hydrolysis of exogenous low-erucic rapeseed oil. The optimum rates of hydrolysis were found at day 4 of germination, pH 8.0, and a temperature of 30 degrees C. The oil (storage triacylglycerols) contained in the seeds of low-erucic rape has also been efficiently hydrolyzed by homogenization of the germinating seedlings in Tris-HCl buffer (pH 8) followed by incubation at ambient temperature. The fatty acids formed undergo very little catabolism via beta-oxidation, and they can be recovered by extraction with hexane or by centrifugation. These findings open up an alternative mild biotechnological approach for the production of fatty acids from plant oils via lipolysis of the seed storage triacylglycerols in situ as opposed to the conventional fat splitting at high temperatures and pressures