Trophic Niche Of Two Strains Of Botryococcus Braunii On Nitrogen

Botryococcus braunii belongs to Chlorophyta, Chlorophyceae, Chlorococcales,Botryococcaeae, Botryococcus, which is a colonial microalgae widespreading in fresh orbrackish waters of all continents, and it is rich in exopolysaceharides, fatty acids andhydrocarbons, so it is regarded as a potential source of renewable fuel. To investigate thetrophic niche of Botryocoecus braunii on nitrogen, the present study concerns on the effectsof three culturing mediums, four nitrogen sources (sodium nitrate, sodium nitrite, ammoniumchloride and urea) and their different concentrations on the growth of B. braunii 764 and B.braunii 765, and cell density (OD₆₈₀), biomass (dry weight), total lipids and hydrocarbonsalso are observed. The results are as follows: (1) Two strains of Botryococeus braunii, B.braunii 764 and B. braunii 765 have obvious selectivity on different culturing mediums.The order of selectivity to the three culturing mediums is accordant, and the fitting order isChu10, Chu13×2 and SE. (2) The four nitrogen sources, NH₄⁺-N, NO₃^--N, NO₂^--N andNH₂CONH₂ selected in this study could be absorbed and utilized by the two algae, butobvious discrepancy of utilization for four nitrogen sources exists between the two algae.The fitting order of utilization for four nitrogen sources in B. braunii 764 is NaNO₃, NaNO₂,NH₂CONH₂ and NH₄Cl; While the order of nitrogen sources promoting the growth of B.braunii 765 is NH₂CONH₂, NaNO₃, NaNO₂ and NH₄Cl. (3) In the condition of fournitrogen sources, NH₄⁺-N, NO₃^--N, NO₂^--N and NH₂CONH₂, B. braunii 764 and B. braunii765 have obvious discrepancy in the growth rate, biomass, total lipids and hydrocarbons; Asconcerning the growth rate, B. braunii 765 grows faster than B. braunii 764; For biomass, inthe condition of NO₃^--N, NO₂^--N and NH₂CONH₂, the biomass of B. braunii 765 is muchhigher than that of B. braunii 764, but in the condition of NH₄⁺-N, the biomass of B. braunii765 is slightly lower; Besides, the highest outputs of total lipids and hydrocarbons of B.braunii 764 are 27.61% and 34.21% respectively, which are much higher than those of B.braunii 765, suggesting B. braunii 764 could be exploited and utilized as a potential energymicroalga. (4) The appropriate range of concentration for NO₃^--N of B. braunii 764 is 2 mMto 10 mM, and the inappropriate one is less than 2 mM; The appropriate range ofconcentration for NO₂^--N of B. braunii 764 is also 2 mM to 4 mM, but the inappropriate oneis less than 2 mM and more than 8 mM; The appropriate range of concentration for NH₄⁺-Nof B. braunii 764 is 1 mM to 4 mM, but the inappropriate one is less than 1 mM and morethan 4 mM; The appropriate range of concentration for NH₂CONH₂ of B. braunii 764 is 0.5 mM to 4 mM, and the inappropriate one is less than 0.5 mM and more than 4 mM. (5) Theappropriate range of concentration for NO₃^--N of B. braunii 765 is 1 mM to 8 mM, but theinappropriate one is less than 1 mM and more than 8 mM; The appropriate range ofconcentration for NO₂^--N of B. braunii 765 is 1 mM to 8 mM, and the inappropriate one isless than 1 mM and more than 8 mM; The appropriate range of concentration for NH₄⁺-N ofB. braunii 765 is 0.5 mM to 2 mM, but the inappropriate one is more than 2 mM; Theappropriate range of concentration for NH₂CONH₂ of B. braunii 765 is 1 mM～4 mM, butinappropriate one is less than 1 mM and more than 4 mM.