Study On Extraction,Refining And EPA Enrichment Of Lipid From Nannochloropsis Sp.

Microalgae,as a major source of unsaturated fatty acids instead of deep-sea fish oil,has the advantages of short growth cycle,fast growth rate and high oil production.Nannochloropsis sp.is rich in polyunsaturated fatty acids and is one of the most potential algae for the production of eicosapentaenoic acid.However,the common algal oil extraction method has a large loss of EPA,low yield,and high content of impurities and pigments in the extracted algae oil,which will greatly affect the quality and appearance of the algae oil.Therefore,it is of great significance to study the extraction,refining and enrichment process of algal oil.This study mainly discusses the extraction,refining process and the process of EPA enrichment purification in algal oil to obtain high-quality and EPA-rich algal oil.It lays a good application foundation for the production of health care products and pharmaceuticals such as EPA using algae oil as raw materials,and provides a certain reference for the industrial application of algae oil.The main research contents and results are as follows:(1)Different organic solvent systems were used for Soxhlet extraction of Nannochloropsis sp.,and the oil extraction rate was used as an indicator to determine the best solvent system and optimize the solvent ratio.Taking into account the oil extraction rate and solvent safety issues,it is determined that n-hexane-ethanol(3:1)is the best solvent ratio.At this time,the oil extraction rate can reach 74.89%.Subcritical butane was used to extract Nannochloropsis sp.,the effects of extraction times,extraction time,extraction temperature and material-liquid ratio on the oil extraction rate of Nannochloropsis sp.were studied,and the process conditions were optimized orthogonally.The optimized process conditions obtained were: extraction times 4 times,extraction time 40 min,extraction temperature 45?,material-liquid ratio 1:8,and the oil extraction rate of Nannochloropsis sp.was 41.01%.The fatty acids of Nannochloropsis sp.oils obtained by the two extraction methods were analyzed.The algae oil obtained by the subcritical butane extraction method has higher EPA content,and can be produced on a large scale.It is safe and efficient,so the use of subcritical butane extraction method is more advantageous.(2)Conventional degumming method,such as hydration method and the acid method was used to degum the oil of Nannochloropsis sp.,the content of phospholipids in algal oil did not change much before and after degumming.The dilute alkali method is used for degumming.At a temperature of 60?,a stirring speed of 300 r/min,the amount of Na OH solution is 0.4%(w/w),the alkali treatment time is 20 min,the degumming rate is 39.5%,the EPA retention rate is 83.6 %,the oil recovery rate is 90.6%,and the degumming effect is better.The polyethersulfone(PES)membrane with a molecular weight cutoff of 10 k Da is used for degumming,the degumming effect is better than all the above methods.The degumming rate is as high as 76.4%,and the EPA retention rate is 91.5%,but it has a greater impact on oil recovery.Comprehensive degumming rate and phospholipid utilization rate,select polyethersulfone(PES)membrane degumming.(3)To study the effect of different decolorizers on the decolorization rate and EPA retention rate of Nannochloropsis sp.oil,and to optimize the decolorization process conditions through single-factor experiments,the better process conditions are: granular activated carbon as decolorization agent,and the amount of decolorization agent was 1.5%,the decolorization temperature is 40?,and the decolorization time is 1.5 h.At this time,the decolorization rate was 75.85%,the EPA retention rate was 79.22%,and the decolorization effect was better.(4)The acid removal method of alkali refining is used to deacidify the Nannochloropsis sp.oil,with the deacidification rate and the oil recovery rate as an index,using orthogonal test to optimize the alkali refining acidization process,the optimization process is: the alkali quality score is 8%,the alkali refining temperature is 50?,the stirring speed is 120 r/min,the alkali refining time is 40 min.At this time,the deacidification rate is 95.37%,the oil recovery rate is 93.96%,and the deacidification effect is the best.(5)The urea embedding method was used to enrich and purify the EPA in the algae oil after refining,and the urea embedding algae oil EPA process was optimized through single factor and response surface test.the resulting optimization process were:1 time for the number of encapsulation,the embedded temperature is-10?,the embedding time is 4.5 h,and the ratio of the soluble ester is 5:1.Under this condition,the EPA content increased significantly,from 7.68% to 22.19% after refining.