Preparation of PUFA concentrates as acylglycerols via enzymatic hydrolysis of hempseed oil (Cannabis sativa L.) in a homogeneous low-water medium

The growing demand for concentrated extracts of PUFA prompted us to undertake the preparation of natural glycerides containing linoleic acid and alpha-linolenic acid from hempseed oil. Hempseed is an exceptionally rich source of essential FA but is still underutilized. Hempseed oil was thus submitted to a lipase-catalyzed hydrolysis in a homogeneous medium based on oil and t-BuOH/water. Seven commercial lipases were screened in this reaction medium, which resulted to be superior to the routinely used biphasic systems in terms of substrate/product solubility and biocatalyst stability. Lipase from Pseudomonas cepacia resulted to be sufficiently selective versus saturated FA and it was thus used to hydrolyze hempseed oil in order to obtain acylglycerols enriched with PUFA. The enzymatic reaction was scaled up and the acylglycerol components were purified and analyzed by GC-FID. In the fraction of monoacylglycerols (yield 22%) the total amount of PUFA reached 85% (against 77% of the crude oil) whereas the content of saturated FA was negligible. The omega-6/omega-3 ratio of the total glyceride component (purified acylglycerols, yield 29%) was maintained in the optimal range (4.6:1) for human nutrition. Therefore, PUFA concentrates from hempseed oil here obtained in the form of natural glycerides could be considered as valuable dietary supplements. The enzymatic method here described allows to directly achieve pure monoglycerides of PUFA with a potential nutraceutical use. This procedure has the advantage to occur under very mild conditions in a homogeneous medium composed of a water miscible green solvent, to be easily scalable and to rely on a standard chromatography purification step.