Extraction Of Microalgae Lipid And Analysis Of Its Fatty Acid Composition

As a class of microorganisms containing chlorophyll a and capably of photosynthesis,microalgae are widely found in soil,ice,lakes,rivers and other natural areas in a large number and variety of species.Under the appropriate conditions,microalgae can grow autotrophically or heterotrophically and accumulate large amounts of biomass within their cells.And biomass could be used to produce biofuels in an economical,environmentally friendly and sustainable way,while biofuels would provide an ideal alternative to fossil fuels.At the same time,algae could be used to produce biological substances such as food or feed additives,pigments and even pharmaceuticals.Based on the above reasons,the research and development of the microalgae industry has received considerable attention in recent years.However,in the processes of producing lipid and grease,the comprehensive utilization of microalgae resources and production benefits are not as satisfactory as they could be,especially the technology of lipid and grease extraction is a shortcoming,leaving a large amount of space for exploration to be studied.In this study,two algal strains preserved in our laboratory were used as research samples.Firstly,based on the cell breakage rate as the indicator,the breakage of Chlorella sp.YZL18 and Scenedesmus sp.YZL17 cells was investigated by ultrasonic method,acid heat method,repeated freeze-thaw method,liquid nitrogen grinding method and enzymatic digestion method.Then,the optimization of the extraction process for microalgae lipid was carried out by the use of lipid extraction rate as the indicator of investigation.Finally,the types and contents of the main fatty acids in microalgae lipids were determined with the utilization of gas chromatography.The predominant findings of this study were as follows.1.The wall breakage rate of Chlorella sp.YZL18 and Scenedesmus sp.YZL17 reached 68.76% and 63.80% respectively after 20 minutes of sonication treatment with an ultrasonic power of 425 W.In the single and the complex enzymatic reactions,YZL17 was treated using only cellulase,with a breakage rate of 56.76%,while YZL18 used a complex of3 enzymes,with a breakage rate of 61.45%,respectively.For the reasons above,ultrasonication and enzymatic digestion would be the preferred ways used for breaking the cell wall.2.The effectiveness of ultrasonication and enzymatic digestion and their combinations on the extraction rate of the lipid from microalgae was investigated.The results showed that the enzymatic digestion followed by ultrasonication was the appropriate treatment method,and the lipid yield of YZL18 and YZL17 could reach 23.51% and 34.16%,respectively.The extraction effect of single-solvent and dual-solvent systems on Chlorella and Scenedesmus lipids was explored.The results showed that cyclopentyl methyl ether(CPME)-ethanol is the best extraction solvent,and the lipid extraction rate of YZL18 and YZL17 reached 85.19%and 86.81%.3.Response surface methodology was used to optimize the extraction conditions of YZL18 and YZL17 on the basis of single factor.The results showed that the optimal extraction conditions of YZL18 lipid were as follows: temperature 51.31 ?,extraction time6.25 h,CPME : ethanol = 0.76?1,the actual extraction rate of lipid was 95.62%.The best conditions for extracting lipid from YZL17 were extraction temperature of 51.19 ?,extraction time of 6.27 h,CPME?ethanol=0.76?1,and the actual measured lipid extraction rate was 94.12%.The results showed that there was a good fit between the predicted value and the actual value,which further confirmed the reliability of the regression model,and provided a basis for large-scale industrial extraction of microalgae lipid.4.Both YZL18 and YZL17 contain higher content of C16-C18 fatty acids.The main fatty acids in YZL18 are C16:0,C18:0,C20:0,and the contents are 17.56%,18.01% and10.95%,respectively.The main fatty acids in YZL17 are C16:0,C18:1,and C20:1,and the contents are 19.31%,13.78%,and 24.62%,respectively.In addition,Docosahexaenoic acid(DHA)was detected in the YZL17 with a relative percentage of 0.62%,and both strains of microalgae have the potential to be used as biodiesel and edible lipids.