| Microalgae is a good promising source for biodiesel because of their rapid growth rates,high lipid content,clean to environment,easy to culture and so on.However,large scale production of microalgae biodiesel is very difficult to realize,due to expensive cost and difficult technical issues of microalgae biodiesel production.Subsequently,it is essential to screen microalgae and optimize cultural conditions for high lipid content.In this paper,five desert microalgae from fresh water of Xinjiang region were purified and identified by their morphology.One oil-rich desert microalgea was screened from five desert microalgae by measuring their indicates of growth and lipid accumulation.Biomass productivity and lipid producivity of Desmodesmus sp.XJ842 was highest.To explore its biological effects of culture medium composition and environmental factors,the effect of culture medium composition(C,N,P)and environmental factors(pH,temperature,light intensity)of Desmodesmus sp.XJ842 on growth rate,biomass productivity,lipid content and lipid productivity were studied.The main results are as follows:1.Identify by their morphology and lipid content of five purified desert microalgae was measured,the results showed that XJD2 and XJD21 were identified as Chlorella vulgaris sp.And XJS81,XJG41 and XJ842 were identified as Desmodesmus sp.Desmodesmus sp.XJ842 was screened due to its rapid growth rates and high lipid productivity.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 was 29.7 mg/L/d,22.1%,8.1 mg/L/d,respectively.And saturated and monounsaturated fatty acids content of it was more than 87%.2.C,N and P were important factors to influence growth rates and lipid production of microalgae,the optimal carbon and nitrogen source was Na2CO3 and NaNO3,respectively.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 respectively was 43.34 mg/L/d,41.58%,17.92 mg/L/d,when the concentration of Na2CO3 was 1.88 mmol/L.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 respectively was 36.85 mg/L/d,38.67%,14.25 mg/L/d,when the concentration of NaNO3 was 1.88 mmol/L.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 was 34.78 mg/L/d,36.68%,12.15 mg/L/d,respectively,when the concentration of K2HPO4 was 1.88 mmol/L.3.To explore the comprehensive influence of C,N,P on the growth and lipid production of Desmodesmus sp.XJ842,the concentrations of Na2CO3,NaNO3,K2HPO4 were optimized recognized by Response surface methodology(RSM).The results showed that the optimized concentrations for Na2CO3,NaNO3 and K2HPO4 were 1.98 mmol/L,48.00 mmol/L and 0.46 mmol/L,respectively.After optimization,the lipid content of XJ842 reached 67.73%,and lipid productivity reached 29.27 mg/L/d.Lipid content and lipid productivity,espectively,raised 2.48 times and 2.61 times compared with before optimization.Saturated fatty acid and monounsaturated fatty acid under the optimum conditions accounted for 90.41%of the total fatty acid.4.Environmental factors(pH,temperature,light intensity)have significant influence to enhance growths and lipid production of Desmodesmus sp.XJ842.The results showed that the biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 was 29.18 mg/L/d,24.15%,8.92 mg/L/d,respectively,when pH was 8.0.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 was 35.11 mg/L/d,30.76%,11.86 mg/L/d?respectively,when temperature was 30?.The biomass productivity,lipid content and lipid productivity of Desmodesmus sp.XJ842 was 37.97 mg/L/d,46.41%,15.30 mg/L/d,respectively,when light intensity was 8800 lux.Desmodesmus sp.XJ842 has a strong adaptability in the high light intensity(6700 lux and 8800 lux)compared with Senedesmus obliquut,whose lipid productivity increased with increasing light intensity.The lipid production of Desmodesmus sp.XJ842 between day and night temperature(35?-17?)was more than normal temperature. |
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