氮源对雨生红球藻绿色生长期细胞生长的影响

Effects of different nitrogen sources on cell growth of Haematococcus pluvialis at “green stage”

摘要:

【背景】雨生红球藻(Haematococcus pluvialis)细胞能合成积累具有超强抗氧化活性的虾青素，是生产高值天然虾青素的优异藻种。【目的】解析不同氮源对雨生红球藻生长的效应，以期建立优化氮素营养提高雨生红球藻生物量和虾青素产量的技术体系。【方法】选用NaNO3和NH4Cl为氮源、辅以pH缓冲液Hepes，培养雨生红球藻藻株797，测试2种不同氮源对雨生红球藻藻液pH、营养生长期(绿色生长期)藻细胞生长、叶绿素含量和生物量等的影响。【结果】NaNO3为氮源培养的雨生红球藻细胞的比生长速率、生物量、叶绿素a和叶绿素b含量均高于以NH4Cl为氮源培养的藻细胞。不同氮源对雨生红球藻培养液的pH值有显著影响，NH4Cl氮源导致培养液pH值降低，然而NaNO3氮源则导致培养液pH值上升。添加pH缓冲液Hepes能有效稳定培养液的pH值，并促进雨生红球藻的生长，尤以NH4Cl为氮源添加Hepes的效果更显著。不同氮源导致雨生红球藻营养生长阶段细胞的生长和生物量等差异主要源于不同氮源引起藻液pH的变化。【结论】添加pH缓冲液Hepes可有效控制藻液pH，进而显著促进以NaNO3和NH4Cl为氮源的雨生红球藻营养生长阶段细胞的生长和生物量积累。

Abstract:

[Background] The unicellular green microalga Haematococcus pluvialis can synthesize astaxanthin which possess super antioxidant properties. H. pluvialis is an excellent microalga for commercial production of high-value natural astaxanthin. [Objective] The current study is to investigate effects of different nitrogen (N) sources on growth of H. pluvialis, with a view to develop the optimized N nutrition technology system for increasing biomass and astaxanthin yield of H. pluvialis. [Methods] Therefore, NaNO3 (NO3–-N) and NH4Cl (NH4+-N) were selected as two different N sources for the culture of H. pluvialis strain 797, respectively. At the same time, Hepes pH buffer was added into the media to keep pH stability. The measurements included pH changes of alga suspension culture media, cell growth rate at vegetative growth stage (“green stage”), chlorophyll content in cells and algal biomass. [Results] The results presented here demonstrated that the specific growth rate, biomass, chlorophyll a and b content in algal cells were higher in the NO3–-N media than in the NH4+-N media. Different N sources showed a significantly effect on pH in H. pluvialis suspension culture media. NH4Cl led to pH reduction in the culture media, whereas NaNO3 resulted in pH increase in the media. The addition of Hepes pH buffer successfully stabilized the pH in the culture media and thus, greatly promoted growth of H. pluvialis, with NH4Cl+Hepes showing much significant in this regard. It is the pH change in the algal suspension culture media caused by two different N sources that resulted in the obvious difference of H. pluvialis’s cell growth, biomass, and other features at “green stage” between the two N source treatments. [Conclusion] Addition of Hepes buffer into the media of either NO3–-N or NH4+-N could effectively stabilize the pH in microalga suspension culture media, and consequently, significantly promoted H. pluvialis’s cell growth and biomass accumulation at vegetative growth stage.