Enrichment of hemp oil with PUFAs by lipase-mediated reactions in a green low-water content medium

Hempseed oil is an exceptionally rich source of linoleic acid (18:2, n-6; LA) and alpha-linolenic acid (18:3, n-3; ALA), two essential polyunsaturated fatty acids (PUFAs) which represent about 70% of the total fatty acid (FA) content. These PUFAs are fundamental in human nutrition since they have a prominent role in the prevention and treatment of cardiovascular diseases, diabetes, rheumatoid arthritis and other inflammatory and autoimmune disorders. Due to nutritional benefits of consuming PUFA concentrates, the market of these products is rapidly growing. We have investigated the enrichment of hempseed oil with linoleic acid (LA) and alpha-linolenic acid (ALA) by lipase-catalyzed hydrolysis. The conventional hydrolytic biphasic system consisting of oil/isooctane/buffer was compared with a homogeneous medium based on oil and t-BuOH/water. The new system appeared to be superior to the classical one in terms of substrate/product solubility and biocatalyst stability. Seven commercial lipases were screened in the new reaction medium. The free fatty acid (FA) composition of the hydrolyzed oil was determined by GC analysis. Selectivity showed by lipase from Pseudomonas cepacia for saturated FAs was exploited to obtain acylglycerols enriched in LA and ALA. The enzymatic reaction was scaled up and the acylglycerol components were purified and analyzed by GC to assess FA composition. In the final product (yield: 29%) the amount of polyunsaturated FAs reached 82% (against 77% of the crude oil) whereas the content of saturated FAs was negligible.