Enzymatic Synthesis Of Triglyceride Rich In Polyunsaturated Fatty Acids From Algal Oil

Docosahexaenoic acid (DHA) and Docosapentaenoic acid (DPA) both belong to polyunsaturated fatty acids, which cannot be synthesized by human, thus having important physiological functions. DHA and DPA extracted from algal oil instead of sea fish oil have advantages like higher content in resource, safety, free from fishy odour and pollution. The DHA and DPA content in natural glycerols or traditional structured glycerols are not high enough to meet people’s demand. Therefore, this paper aimed at preparing triglycerides rich in polyunsaturated fatty acids like DHA and DPA, which is achieved by the choose and analysis of resouces, purification of fatty acids, control of solvent-free esterification and purification of products:(1) As to the enrichment of PUFAs like DHA and DPA, a new enzymatic dynamics method based on the substrate specificity of lipase (i.e. the difference of esterification reaction rate between small molecule fatty acids and PUFAs with alcohol) is developed. Dodecnaol is used as a substrated to selectively react with impurities to enrich the PUFAs of the alge oil with an initial PUFAs content of 50%. When the mass ratio of dodecnaol to FFAs being 1:0.16, enzyme amount being 4% of the mass of FFAs, the reaction is carried out under 45℃ for 3h, and extracted by 95% ethyl alcohol, DHA+DPA content can reach 90%. Compared traditional enrichment methods, enzymatic dynamics one has the advantages of little waste water and poisonous agents. Combination of urea complexation, enzymatic dynamics and silica gelcolum chromatography can enhance the purity of PUFAs to 99%.(2) A solvent free system of enzymatic synthesis of high content triglyceride rich with DHA and DPA is developed. The viscosity of glycerol, low reaction rate of huge molecule and water removal are studied. Vaccum is used to remove water and the content of triglycerides can reach 80% under the following conditions:the mole ratio of glycerol to PUFAs being 1:3.5, enzyme amount being 24000U/per gram PUFAs, initial water content being 0.8-1.0aw, vaccum degree being 50-100mabr,50℃,200rpm,48h. This result is better than the 67% triglyceride content by interesterification according to relavant literatures.(3) Extraction is used to enrich trilycerides with rich DHA and DPA. For the traditional silica gelcolum chromatography, the content of triglycerides can reach 99% with a yield of 26%. A new extraction method is developed to enrich the content of triglycerides to 96% by reextration with a yield of 71% according to the following conditions:the voloume ratio of the products to 95% ethyl alcohol is 1:2. It has the advantages of less time, larger handing capacity and being environmental friendly.(4)Based on the above research, a newly lecithin rich in PUFAs is also studied tentatively, wherein DHA and DPA content reaching 65%, laying a foundation for further study.