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In recent years, due to the increasing depletion of oil resources and its environmental pollution caused by burning biodiesel as a wide variety of sources of renewable energy, the development and application attracted widespread attention. Microalgae photosynthetic efficiency of a primitive plant with large biomass, high in fat content, the growth cycle is short, easy to mass culture, is an excellent material for biodiesel production. However, due to the high cost of production, microalgae biodiesel has yet to achieve commercial production, a large number of studies have shown that the microalgae growth and accumulation of fatty acids and environmental control. This paper studies the indole acetic acid (IAA) growth and fatty acid composition of microalgae, more nitrogen limitation added to the culture conditions and medium sodium tungstate and sodium molybdate treatment, microalgae fatty acid composition changes, designed by changing the culture conditions, to explore the possibility of a large number of rapid growth of microalgae oil enriched to provide a theoretical basis and technical support for the mass production of microalgae biodiesel. First, select the studies have reported that high-fat filter the rapid growth of algae Chlorella and oculata are easy to cultivate. Laboratory microalgae and marine areas separated six kinds of algae growth comparison, screened two kinds of microalgae, respectively oculata, Chlorella C7. One of IAA as a plant hormone can promote and stimulate many unicellular algae growth, this experiment is higher than the growth rate and the final cell density and optical density comparison, suitably added to the the IAA algal cells can quickly reach the exponential growth phase, to obtain a higher biomass. Oculata, The chlorella C7 growth-promoting the best concentration to 0.1 mg / L, 0.25mg / L, IAA two kinds of microalgae fatty acid synthesis does not promote high concentration of IAA inhibit the synthesis of the EPA. , Two kinds of microalgae fatty acid content was significantly higher in the nitrogen-free culture conditions. Oculata under nitrogen limitation culture conditions, 16:0,16:1,18:1 increase in the proportion of the total fatty acids, while the ratio of 14:0,20:4,20:5 decreased, Processing 96h, 4 kinds of main fatty acid content increased by 17.30%; the chlorella C7 in a nitrogen-free medium, 16: (4n-3) and 18:1 (n-9) in the proportion of the total fatty acids increased, 18:3 (n-3) and 20:5 (n-3) ratio has decreased, the processing 96h, 4 kinds of main fatty acid content of 1.18% increase. Nitrate reductase is an important regulator of the enzyme and the rate-limiting enzyme in the nitrogen metabolism process, can directly regulate the original nitrate to adjust nitrogen metabolism, and sodium tungstate is a nitrate reductase inhibitor, can inhibit the activity of nitrate reductase, restrict nitrogen absorption. The results of this study show that adding different concentrations of sodium tungstate culture microalgae Haematococcus micro intended 16:0,16:1,18:0,18:1 has increased the proportion of the total fatty acids and 14:0, 20:4,20:5 ratio decreased; chlorella cells 16:0,18:1 (n-9) to increase the proportion of the two fatty acids in the total fatty acids, 18:3 (n-3) , 20:5 (n-3) ratio decreased fatty acid accumulation trend is consistent with the nitrogen-free culture conditions, the cells increase in the degree of saturation of fatty acids, unsaturated fatty acids decreased, therefore adding sodium tungstate reaches the limiting effect of nitrogen. The sodium molybdate nitrate reductase activator of experiments to explore the impact of sodium molybdate microalgae fatty acid composition, experiments show that adding sodium tungstate, slightly intends to the ball in algal cells 16:0,20:5 two kinds of fatty acids in the total fatty acid content increased, especially EPA was significantly increased, as opposed to nitrogen-limited culture and adding sodium tungstate culture results; C7 cell chlorella 16:0,18:1 of (n-9) in the proportion of the total fatty acids is significantly improved, 16: (1n-7), 16: (4n-3), 18:2 (n-6) and 18:3 (n-3) significantly decreased the proportion of the total fatty acids oleic acid content increased significantly, alpha-linolenic acid content decreased, increase in the intracellular fatty acid content and the nitrogen-limited culture, add sodium tungstate on chlorella fatty acid synthesis similar to the role of sodium tungstate oculata and small C7 fatty acid synthesis in the Haematococcus role there is a significant difference, indicating different types of microalgae are not identical, the fatty acid metabolism and biosynthesis pathway. Finally, this study suggests that, the oculata relative to the high fat content of chlorella C7, the role of nitrogen limitation is more suitable for large-scale production of microalgae biodiesel. Route is as follows: 0.1 mg / L IAA culture to the exponential growth phase (about 8 days) to reach a certain biomass Add 1mmol / L of sodium tungstate with nitrogen limitation process (about 3 days), microalgae fatty acid added in the initial stage of growth a lot of accumulation, it will ensure the biomass, but also can improve the lipid content of microalgae, and this method is simple, production feasibility, to improve experimental basis and technical support for large-scale cultivation of microalgae.
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