Screening Algae Strains Of Chlorella Sp. And Dunaliella Salina With Resistance To Oil Pollution And Their Lipid Enrichment By Using Petroleum Hydrocarbons

Due to the energy crisis and the destruction of the ecological environment by thecombustion of fossil fuels, researches of renewable energy are widely concerned. Biodiesel, akind of biomass energy with less pollution, has become the most developed renewable energy.Compared with traditional oil crops, only water, light and some simple nutrition are neededfor the growth of algae. Production of biodiesel and microalgae fuel with marine microalgaeas raw materials has become a research hotspot. In this study, a plan was put in practice thatscreening algae strains of Chlorella sp. and Dunaliella salina with resistance to oil pollutionand whether they can enrich lipid in cells by using petroleum hydrocarbons. Chlorella sp. andDunaliella salina are two common green microalgae but with high fat. To screen the originalalgae strains of Chlorella sp. and Dunaliella salina, single-cell separation technology andultraviolet mutation breeding techniques were used in this study. To get the growth-dominantalgae strains, biuret method, sulfuric acid anthrone method and spectrophotometer were usedto analyze their biochemical components. And respectively predominant strains of the growthof the two microalgae with oil pollution resistance, and then the growth-dominant algae werecultured in oily seawater with different oil concentrations. The contents of the compoundswith conjugated hydrocarbon and petroleum aromatic hydrocarbons were determinedrespectively by UV spectrophotometry and fluorescence spectrophotometry. The fat contentof the microalgae cells was measured by the Soxhlet extraction method. Using gaschromatography and mass spectrometry analyzed the effect of benzene and toluene on lipidenrichment of two microalgae cells. The results are as follows:1. Screening algae strains of Chlorella sp. and Dunaliella salina with resistance to oilpollution.(1) Each five growth-dominant strains of Chlorella sp. and Dunaliella salina wereacquired by single-cell separation technology, and among them Chlorella sp. M4andDunaliella salina M02were respectively selected as the dominant strains for UVspectrophotometry by analyzing their biomass and growth rate.(2) The best UV-mutagenesis condition of Chlorella sp. and Dunaliella salina wasobtained by the pre-mutagenic examinations. That is as follows:30W UV lamp irradiation,vertical distance of15cm and irradiation time of20min. (3) The two algae strains with resistance to oil pollution are obtained, respectivelyChlorella sp. A16and Dunaliella salina A001by the analysis of the growth curves and thecontent of intracellular and extracellular proteins, intracellular and extracellularpolysaccharides and pigments.2. Lipid enrichment of Chlorella sp. and Dunaliella salina by the degradation ofpetroleum hydrocarbons(1) UV spectrophotometry and fluorescence spectrophotometric analysis showed thatChlorella sp. and Dunaliella salina were able to effectively degrade petroleum hydrocarbonsin oily seawater with1.5-10.0μg/mL oil, and the degradation rates of the compounds withconjugated hydrocarbon were respectively25.3-35.5%and17.9-24.0%, the degradation ratesof petroleum aromatic hydrocarbon were respectively22.1-30.2%and18.7-26.2%. Both ofpetroleum hydrocarbons were degraded best in the oily seawater with3.5μg/mL oil. Thedegradation rate of Chlorella sp. was higher than Dunaliella salina.(2) Soxhlet extraction results showed that the fat content of the cells cultured in the oilyseawater with3.5μg/mL oil is the highest among the experimental oil concentrations. Andthen the fat contents of algal cells were14.0%and25.5%of the cell dry weight and both1.5times and1.2times of control respectively when cultured in the seawater with3.5μg/mL oil.3. Lipid enrichment of Chlorella sp. and Dunaliella salina increased by benzene andtoluene(1) GC-MS results showed that the benzene and toluene utilization of both Chlorella sp.and Dunaliella salina were very low. The utilization of Chlorella sp. is1.15-1.50%and1.50-1.80%, the utilization of Dunaliella salina is1.18-1.65%and1.62-2.20%.(2) Soxhlet extraction results showed that fat contents of algal cells were increased7.7-16.3%and11.6-19.3%of control, respectively.