| Marine microalgae are most primary producer in marine ecosystem, and also are most important sources of marine bioactive materials. Most marine microalgae are able to biosynthesis polyunsaturated fatty acids (PUFAs) especially long-chain polyunsaturated fatty acids (LC-PUFAs) which are essential for normal physiological functions and play an important role in prevention and treatment of a number of human diseases such as heart and inflammatory diseases. To screen microalgae species enriched LC-PUFAs such as EPA and DHA and to enhance the production of these special fatty acids are one of most attractive and important in the fields of marine biology and lipids related. In this study, marine microalga previously named as "Chlorella sp." and numbered with 1061 by Institute of Oceanology, the Chinese Academy of Sciences, was selected as experimental materials, and of this alga the composition and content of glycerolipid and fatty acid, effect of exogenous carbon source of glucose and antioxidant reagent of sodium thiosulfate on lipids and chemotaxonomy on the basis of lipids, were studied and the results showed in the below.Marine microalgae are wildly used in marine aquaculture and lipids are one of major issue to evaluate their nutrition. Firstly we analyzed the species and composition of glycerolipids and fatty acids in Chlorella sp. named and presented by Institute of Oceanology, the Chinese Academy of Sciences. The results showed that this alga also contain two groups of glycerolipids, i.e., non-polar lipids (NPL) mainly triacylglycerol (TAG); polar-lipids (PL) of 10 species. Under common culture condition (temperature 23 ℃; light, cycle L/D14:10, intensity 60μmol·m-2-S-1), relative content of TAG of total lipids came to about 31% and PL did 69%. Ten species of PL were found in Chlorella sp., and 9 of 10 species were identified clearly respectively as monogalactosyldiacylglycerol(MGDG), diagalactosyldiacylglycerol(DGDG), sulfoquinovosyldiacylglycerol (SQDG), phosphatatidylglycerol (PG), phosphatidylethanolamine (PE), phosphatidylchloine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), diacylglyceryltrimethylhomoserine (DGTS) and one unsure identified but probably chlorosulfolipid (CSL) contained chloroform and sulfur. LipidsMGDG, DGDG, SQDG and PG were major components of photosynthetic thylakoid membranes, and these lipids were also major of PL, while betaine lipids DGTS and phospholipids PC were major of nonplastidial membranes lipids. Fatty acids C16:0, C16:l and C20:5 (EPA) were dominant in content, the later mainly distributed in MGDG, DGDG and DGTS and reached to about 7% in TAG.Marine Chlorella sp. 1061 was before identified as one member of genus Chlorella of Chlorophyeae, nevertheless the characteristics of pigment, PL and fatty acids were obviously divers from these of members of Chlorella. Chlorophyll b is one of major photosynthetic pigments in green algae, and 16:4 (n-3) and 18:3 (n-3) are major fatty acids in this group of algae. However these characteristic compounds of green algae were not observed in Chlorella sp.. DGTS and EPA are often common in marine microalgae, but they have not been found in Chlorella so far, yet the two compounds were existed in high content in Chlorella sp.. But these characteristics of lipids contrasted to Chlorella are well consistent with these of members of Eustigmatophyceae Nannochloropsis. So on the basis of lipids, in term of chemotaxonomy, marine Chlorella sp. 1061 should be belong in Nannochloropsis, rather than in Chlorella. This alga may be Nannochloropsis sp, nevertheless, we still used the Chlorella sp. to name this alga before there is no further evidence and confirmation of authorities.This paper also demonstrated that the lipid DGTS enriched in EPA and the fatty acid was confined at sn-2 position of glycerol of DGTS. This alga contained DGTS as a major component and PC as a major phospholipid; this is contrasted to the hypothesis DGTS is used as substitute of PC on the basis of the fact that many DGTS-producing algae ha...
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