The Research Of Desert Chlorella (Chorella Sp.) Oil Properties And Its Regulation Mechanism

Objective:This paper took a Chlorella which had isolated from the Taklimakan Desert as the research object,PEG6000 was used to simulate different drought condition,the effect of different water stress on the growth and lipid accumulation of Chlorella was compared by measuring the absorbance(OD680),cell dry weight,growth rate,soluble protein content,lipase activity and total lipid content.Established a two-dimensional electrophoresis system which is suitable for Chlorella.In order to explore the mechanism of desert chlorella under water stress,two-dimensional gel electrophoresis was used to compare and analyse proteomic changes of desert chlorella between water stress and normal processing conditions.Methods:Weighing method had been used to measure the cell dry weight of Chlorella,phosphoric acid vanillin method had been used to measure total lipid content of Chlorella.The performances of protein extraction methods from desert chlorella were compared between TCA/acetone precipitation method and Trisol extraction,the chose pH gradient gel strips and protein loading volume were also optimized.Twodimensional gel electrophoresis and MALDI-TOF/TOF-MS were used to compare and analyse proteomic changes of desert chlorella between water stress and normal processing conditions.Results and Conclusions:1.Water stress had an inhibitory effect on the growth of Chlorella and the synthesis of soluble protein,but the amount of PEG6000 5% water stress condition played a role in promoting the growth during the early growth of Chlorella,the results showed that the cell dry weight and soluble protein content increased significantly.Under water stress,the biomass of Chlorella water,soluble protein content,lipase enzyme activity,total lipid content increased gradually from the logarithmic growth phase,and reached a maximum in the stable period.The growth of Chlorella was significantly inhibited with stress level increased.Compared with the control group,the biomass and the content of soluble protein decreased significantly.The lipase activity and total lipid content increased with the increase of water stress and the extension of culture time,and reached the maximum when the amount of PEG6000 was 20%.Chlorella can't grow exponentially when the amount of PEG6000 was 30%,the growth and lipid synthesis is severely inhibited.Chlorella can change soluble protein and total lipid content to start the osmotic adjustment mechanism to maintain normal physiological function when it faced with water stress.2.Our results showed that Trisol extraction could obtain high pure protein.The improved 2-DE system for desert chlorella were come out as follows: Linear IPG strips of 24 cm in length with the pH ranges from 3 to 10,500 ?g loading volume,80 000 Vh of IEF time.Linear IPG strips of 24 cm in length with the pH ranges from 4 to 7,1000 ?g loading volume,80 000 Vh of IEF time.3.By using two-dimensional gel electrophoresis and MALDI-TOF/TOF-MS to compare proteomic changes of Chlorella between water stress and normal processing conditions in process of lipid accumulation.Compared with the control group,there were 32 statistically significant protein s pots.The 12 proteins of all presenting spots were up-regulated,and 12 proteins were down-regulated,8 proteins were first downregulated and up-regulated.In finally,there were 29 differentially expressed protein spots identified by 2-DE and MALDI-TOF/TOF-MS.These proteins were divided into 7 categories according to their role in biologic al metabolism,involved in energy generation and transformation related protein(3 spots),metabolism related protein(4 spots),antioxidant related proteins(1 spots),photosynthesis related protein(3 spots),protein transport and cell structure related protein(2 spots),resistance related protein(2 spots),unknown protein(14 spots).The expression of these proteins affected the lipid accumulation of Chlorella,many proteins directly or indirectly involved in the lipid metabolism of Chlorella desert such as ATP synthase,ATP-dependent zinc metalloprotease FTSH 5,TCP-1/cpn60 chaperonin,putative ribulose-phosphate 3-epimerase,glyceraldehyde-3-phosphate dehydrogenase,Aconitate hydratase.