Selection Of Rich Lipids-Microalgae And The Research On The Factors Affecting The Lipid Content And Lipid Composition Of Microalgae

With the population increasing and scarcity of the natural resource, people have to find a renewable, biodegradable, and non-toxic fuel to replace the fossil fuel. The conventional oil resource such as plant lipids and anminal fat can not satisfy people's demand, so finding a new kind of oil raw material is very important. Microalgae is one kind of the important raw materials due to the advantages such as high contents of lipids and the unoccupation of plantation.The contents of lipids of microalgae are different according to different kinds of microalgae and affected by various environmental factors. In this study, a high efficiency, easy and suitable method of lipids exacting was found by comparing different kinds of exacting methods. The rich lipids-microalgae were found out through determining the total fat contents of 12 strains of microalgae and the lipid yields were calculated according to the growth cycle and biomass. In addition, fatty acid composition of four microalgae were determined by GC-MS. The results showed that: 1)Isochrysis sp., Amphidinium sp., Heterosigma sp. and Prorocentrum sp. were rich lipids-microalgae with the total lipid content accounting for 45%,36.5%,35% and 29.5% of the total cells dry weight respectively. 2)Biomass was one of the important factors which affected the lipid yields and the lipid yields of four rich lipids-microalgae were 5.58 mg·d^-1·L^-1,7.57mg·d^-1·L^-1,7.44mg·d^-1·L^-1 and 8.36 mg·d^-1·L^-1 respectively. 3)The major fatty acids in four rich lipids-microalgae were C16-C18(more than 68% of total fatty acid). From the results, they were fit for chemical composition of biodiesel.The influence of nitrogen,phosphorus,and silicon nutrition on the growth rate and lipid content of Isochrysis sp. was studied by single factor experiment. The results showed that Isochrysis sp. grew slowly in low level of nitrogen,phosphorus nutrition but the content of oils was high. When the NaNO3 levels were 150μM, 600μM and 3000μM,the lipid contents were 63.4%,47.3% and 20.5% respectively and the highest lipid yield was 63.4mg·L^-1 in the 600μM level. When the NaH2PO4 levels were 6μM, 25μM and 36μM,the lipid contents were 55.1%,40.5% and 37.8% respectively and the highest lipid yield was 64.3mg·L^-1 in the 36μM level. Silicon nutrition did not affect much on the Isochrysis sp. growth, and the lipid content and lipid yield were 37.8% and 42.2mg·L^-1 with silicon which were higher than silicon scarcity.