微藻培养基平衡pH的研究

平衡pH是培养基中二氧化碳分压与空气中二氧化碳分压平衡时的pH，是微藻培养基的一个重要特征参数。选用常用的三种微藻培养基:BG11培养基、BBM培养基和Zarrouk培养基，使用鼓泡通入空气的方法，研究碳源、氮源、磷源浓度和盐度对培养基平衡pH的影响。结果如下:在NaHCO3浓度016.8 g/L范围内，三种培养基的平衡pH都随碳源浓度的增加而升高；NaNO3浓度在02.5 g/L范围内，对培养基平衡pH没有影响；0.1 g/L KH2PO4使BG11培养基的平衡pH稍有升高，与之相反，BBM培养基的平衡pH稍有下降，进一步提高磷（P）浓度（最高0.4 g/L），BG11培养基和BBM培养基的平衡pH不再变化；P浓度变化对Zarrouk培养基的平衡pH没有影响；三种培养基的平衡pH都随盐度的升高而降低。碳源浓度是影响培养基平衡pH的最主要因素，平衡pH与碳源浓度的关系可以用回归方程y=0.3504ln（x）+8.9647（R2=0.9708）表示，氮源浓度对平衡pH没有显著影响，磷源浓度和盐度对培养基平衡pH有影响，但影响不大。控制藻液pH不低于平衡pH，可以提高微藻培养中CO2的利用效率，有利于实现微藻CO2生物固定的环境效益。  

STUDIES ON EQUILIBRIUM PH VALUES OF MICRO ALGAL MEDIUM

Equilibrium pH value, one of the important chemical parameter of medium, is the pH value when CO2 partial pressure in the micro alga medium equals to CO2 partial pressure in the air. The three mostly used medium (BG11 medium, BBM medium and Zarrouk medium) were used to study the effects of carbon, nitrogen and phosphorus concentration and salinity on the equilibrium pH value by air bubbling aeration of the medium. Our results demonstrated that the increased NaHCO3 concentration in the range of 016.8 g/L enhanced the equilibrium pH values of all three medium. In the concentration range of 02.5 g/L, NaNO3 had no significant effect on equilibrium pH value of these three medium. 0.1 g/L KH2PO4 raised the equilibrium pH value of BG11 medium, but decreased it in BBM medium. The further increased P concentration (maximum 0.4 g/L) did not regulate the equilibrium pH value of both BG11 and BBM medium. The P concentration in the range of 00.4 g/L did not affect the equilibrium pH value of Zarrouk medium. The salinity in the range of 034 decreased the Equilibrium pH value of all three medium. Carbon concentration is the most important factor to influence the equilibrium pH value of micro algae medium, and the relationship between equilibrium pH value and carbon concentration can be described with the regression equation: y=0.3504ln(x)+8.9647 (R2=0.9708). N concentration had no significant effect on equilibrium pH value. P concentration and salinity had limited impact on equilibrium pH value. The efficiency of CO2 utilization will be improved at higher pH value compared with the equilibrium pH value. These results support the environmental benefit of biofixation of CO2 by micro algae.