Isolation And Screening And Optimizing Culture Of Microalgae With High-lipid Contents In Shanxi Province

Mankind is faced with two problems of energy shortage and environmental pollution that are caused by accelerated consumption of fossil energy. Finding a clean and renewable energy becomes very urgent. Biodisel possess many advantages, renewable raw materials, excellent combustion and degradation of the product. So biodisel is considered to be a good substitude for fossil energy. In recent years, biodisel has achieved a large-scale industrial production at home and abroad. Its source of raw materials is mainly jatropha, rapeseed, palm and so on that have significant drawbacks. Microalgae are widely present in the various bodies of water, in which many types have fast growth and high lipid contents. Because of these, microalgae are suitable as a source for biodisel.A lot of basic research on microalgae biodisel have been done by domestic and foreign scholars.But the cultivation of raw materials, high cost of havest and low lipid contents still become the key reasons that hinder biodisel’development. Screening and cultivating high lipid algae become our top priority. This study was designed to isolate and screen high-fat algae from the natural environment, and then use optimizing cultural method to improve the oil yield of algae. In the end, we can provide a theoretical basis for the selection of raw materials for biodisel and provide some data to support its large-scale production.After expanding culture, high-lipid algae are screened.The biomass of32strains of microalgae vary between48.9mg/L-422.2mg/L, which is determined by dry weight method. In this study, Chloroform-methanol extraction and Nile red fluorescent staining method were combined to state lipid contents of the32strains of microalgae. The results showed that the total lipid contents of all strains were in the range of5.4-30.1%dw, fluorescence value in unit volume were in the range of4.1-181.5. According to microalgae’s lipid productivity, we have screened3strains of microalgae that may be potential oil-producing candidates in Shanxi province. These three strains of microalage include NY017(Dunaliella salina), NY023(Nitzschia linearis) and NY025(Nitzschia paled). And their lipid productivity were3.25mg/L-d,3.03mg/L-d and2.11mg/L-d respectively.The two methods of lipid determination showed that Nitzschia palea has a higher lipid contents, therefore the optimizing cultural method was used to improve the oil yield of this algae. At first temperature and light intensity were optimized. Then under these conditions, N, P, Si orthogonal experiment was designed to explore the impact of the three factors on the growth and neutral lipid content. The results showed that, the optimal temperature for the growth and neutral lipids accumulation of N. palea are20℃. The optimal light intensity for the growth of N. palea is4000lx, while5000lx is more conductive for neutral lipids accumulation. The orthogonal experiment results indicated that the growth of N. palea was significantly influenced by N、P、 Si、N×P、N×Si, and the optimum conditions were obtained when N80mg/L, P120mg/L, Si100mg/L. Neutral lipids accumulation was significantly influenced by N、Si、N×P、NxSi, and the optimum conditions were obtained when N80mg/L, P120mg/L, Si50mg/L. To some degree, the accumulation of neutral lipids can be increased by the lack of N and Si.