Pacific Northwest National Laboratory, Marine Sciences Laboratory, Sequim, Washington 98382;, USA.
Biotechnol Bioeng. 2013 Jun;110(6):1583-94. doi: 10.1002/bit.24814. Epub 2013 Jan 17.
A microalgae biomass growth model was developed for screening novel strains for their potential to exhibit high biomass productivities under nutrient-replete conditions in photobioreactors or outdoor ponds. Growth is modeled by first estimating the light attenuation by biomass according to Beer-Lambert's Law, and then calculating the specific growth rate in discretized culture volume slices that receive declining light intensities due to attenuation. The model uses only two physical and two species-specific biological input parameters, all of which are relatively easy to determine: incident light intensity, culture depth, as well as the biomass light absorption coefficient and the specific growth rate as a function of light intensity. Roux bottle culture experiments were performed with Nannochloropsis salina at constant temperature (23°C) at six different incident light intensities (10, 25, 50, 100, 250, and 850 µmol/m(2) s) to determine both the specific growth rate under non-shading conditions and the biomass light absorption coefficient as a function of light intensity. The model was successful in predicting the biomass growth rate in these Roux bottle batch cultures during the light-limited linear phase at different incident light intensities. Model predictions were moderately sensitive to minor variations in the values of input parameters. The model was also successful in predicting the growth performance of Chlorella sp. cultured in LED-lighted 800 L raceway ponds operated in batch mode at constant temperature (30°C) and constant light intensity (1,650 µmol/m(2) s). Measurements of oxygen concentrations as a function of time demonstrated that following exposure to darkness, it takes at least 5 s for cells to initiate dark respiration. As a result, biomass loss due to dark respiration in the aphotic zone of a culture is unlikely to occur in highly mixed small-scale photobioreactors where cells move rapidly in and out of the light. By contrast, as supported also by the growth model, biomass loss due to dark respiration occurs in the dark zones of the relatively less well-mixed pond cultures. In addition to screening novel microalgae strains for high biomass productivities, the model can also be used for optimizing the pond design and operation. Additional research is needed to validate the biomass growth model for other microalgae species and for the more realistic case of fluctuating temperatures and light intensities observed in outdoor pond cultures.
开发了一种微藻生物质生长模型，用于筛选新型菌株，以评估它们在光生物反应器或户外池塘中营养充足条件下表现出高生物质生产力的潜力。生长通过首先根据比尔-朗伯定律估计生物质的光衰减，然后计算由于衰减而接收递减光强度的离散培养体积切片中的比生长速率来建模。该模型仅使用两个物理和两个物种特异性的生物输入参数，所有这些参数都相对容易确定：入射光强度、培养深度，以及生物质的光吸收系数和特定生长速率作为光强度的函数。在不同的入射光强度（10、25、50、100、250 和 850 μmol/m(2) s）下，在恒定温度（23°C）下用 Nannochloropsis salina 进行了 Roux 瓶培养实验，以确定非遮光条件下的特定生长速率和作为光强度函数的生物质光吸收系数。该模型成功地预测了不同入射光强度下 Roux 瓶分批培养中光限制线性阶段的生物质生长速率。模型预测对输入参数值的微小变化较为敏感。该模型还成功地预测了在恒定温度（30°C）和恒定光强度（1650 μmol/m(2) s）下以分批模式运行的 LED 照明 800 L 跑道池塘中培养的 Chlorella sp.的生长性能。氧浓度随时间的测量表明，在暴露于黑暗后，细胞至少需要 5 秒才能开始暗呼吸。因此，在高度混合的小型光生物反应器中，由于细胞快速进出光，培养物中无光区的暗呼吸导致的生物质损失不太可能发生。相比之下，生长模型也支持，由于暗呼吸，在相对混合较差的池塘培养物的暗区中会发生生物质损失。除了筛选具有高生物质生产力的新型微藻菌株外，该模型还可用于优化池塘设计和操作。需要进一步的研究来验证该模型在其他微藻物种中的生物质生长模型，以及在户外池塘培养中观察到的波动温度和光强度的更实际情况下。
