Nitrogen source uptake and associated pH changes influence growth and biomass composition in microalgae isolated from a polluted river

The data collection are the raw data analyzed, and used to develop the following study: "Nitrogen source uptake and associated pH changes influence growth and biomass composition in microalgae isolated from a polluted river". All the material and methods are depicted in the corresponding manuscript. Microalgae exhibit diverse responses to various nitrogen forms in natural environments, affecting growth rates, biomass yields, composition, by-product production, and nutrient utilization efficiency, which vary among species and strains. In the present study, the growth of two microalgae species was investigated with different nitrogen sources to study their effect on these parameters. In particular, the evolution of several parameters associated with microalgal cultures was examined in relation to the nitrogen source and the pH of the culture medium. Furthermore, simple alternative techniques for estimating biomass growth in microalgal cultures based on nitrogen consumption and/or acid/base titrations are proposed. CI (Parachlorella kessleri) and DIII (Desmodesmus communis) were isolated from the Reconquista River, a polluted watercourse in Buenos Aires, Argentina. CI showed higher productivity, faster biomass growth, and increased extracellular polymeric substances (EPS) production, which promoted cell agglomeration, when cultured in culture medium with NO3- as the nitrogen source, compared to cultures with NH4+ as the nitrogen source. On the other hand, DIII grew only when cultured in medium with NO3-, reaching a maximum growth rate comparable to that of CI in culture medium with NO3-. Growth inhibition in cultures containing NH4+ was attributed to pH decrease associated with NH4+ uptake rather than NH4+ effects. Both species exhibited an increase in the C/N ratio. Under N starvation DIII accumulates N-free substances like lipids and starch in both culture conditions, at controlled pH (≈7). In contrast, the results for CI showed a more pronounced increase in the C/N ratio when cultured in medium containing NO3-, which was attributed to the formation of EPS. These variations in the composition of the microalgae biomass and the occurrence of cellular agglomeration throughout a culture suggest that different biomass estimation techniques may not be directly comparable across different phases of a culture. In this sense, in the present work it was demonstrated that for certain conditions, it is possible to accurately estimate growth from the consumption of nitrogen, and from the variation in the concentration of OH- and/or H+ of the culture medium.

本数据集收录的为本次研究所分析并使用的原始数据，相关研究主题为《氮源摄取与伴随pH变化对污染河流分离微藻生长及生物质组成的影响》。所有实验材料与方法均详见对应发表论文。
微藻在自然环境中对不同形态氮源呈现多样响应，该响应会影响其生长速率、生物质产量、组成成分、副产物生成及养分利用效率，且这类响应因物种与菌株而异。
本研究针对两种微藻物种，探究不同氮源对上述各项参数的影响。具体而言，本研究围绕氮源与培养基pH值，考察了微藻培养体系中多项关联参数的动态变化。此外，本研究还提出了基于氮消耗和/或酸碱滴定法，估算微藻培养体系生物质生长量的简易替代方法。
本研究所用的CI（原壳小球藻（Parachlorella kessleri））与DIII（普通集星藻（Desmodesmus communis））均分离自阿根廷布宜诺斯艾利斯的污染河道雷孔基斯塔河（Reconquista River）。
与以NH4+为氮源的培养体系相比，CI在以NO3-为氮源的培养基中培养时，展现出更高的生产力、更快的生物质生长速率，且胞外聚合物（EPS，extracellular polymeric substances）产量更高，该特性促进了细胞聚集。
相较之下，DIII仅能在以NO3-为氮源的培养基中生长，其最大生长速率与CI在NO3-培养体系中的最大生长速率相当。含NH4+的培养体系中出现的生长抑制现象，归因于NH4+摄取过程伴随的pH下降，而非NH4+本身的直接作用。
两种微藻的碳氮比（C/N）均出现上升。在可控pH（≈7）的两种培养条件下，处于氮饥饿状态的DIII均会积累脂质、淀粉等不含氮物质。
与之相反，CI在以NO3-为氮源的培养基中培养时，其碳氮比的提升更为显著，该现象归因于EPS的生成。微藻生物质组成的上述变化，以及培养过程中出现的细胞聚集现象，表明不同的生物质估算方法在培养的不同阶段之间可能无法直接通用。
基于此，本研究证实，在特定条件下，可以通过氮消耗量以及培养基中OH-和/或H+浓度的变化，精准估算微藻的生长量。