Benvenuti Giulia, Lamers Packo P, Breuer Guido, Bosma Rouke, Cerar Ana, Wijffels René H, Barbosa Maria J
Bioprocess Engineering, AlgaePARC, Wageningen University, P.O. Box 16, 6700 AA Wageningen, The Netherlands.
Microbiology, Food Science and Technology, Biotechnical Faculty, University of Ljubljana, Večna pot 111, 1000 Ljubljana, Slovenia.
Biotechnol Biofuels. 2016 Mar 16;9:64. doi: 10.1186/s13068-016-0475-4. eCollection 2016.
For a commercially feasible microalgal triglyceride (TAG) production, high TAG productivities are required. The operational strategy affects TAG productivity but a systematic comparison between different strategies is lacking. For this, physiological responses of Nannochloropsis sp. to nitrogen (N) starvation and N-rich medium replenishment were studied in lab-scale batch and repeated-batch (part of the culture is periodically harvested and N-rich medium is re-supplied) cultivations under continuous light, and condensed into a mechanistic model.
The model, which successfully described both strategies, was used to identify potential improvements for both batch and repeated-batch and compare the two strategies on optimized TAG yields on light (amount of TAGs produced per mol of supplied PAR photons). TAG yields on light, for batch, from 0.12 (base case at high light) to 0.49 g molph (-1) (at low light and with improved strain) and, for repeated-batch, from 0.07 (base case at high light) to 0.39 g molph (-1) (at low light with improved strain and optimized repeated-batch settings). The base case yields are in line with the yields observed in current state-of-the-art outdoor TAG production.
For continuous light, an optimized batch process will always result in higher TAG yield on light compared to an optimized repeated-batch process. This is mainly because repeated-batch cycles start with N-starved cells. Their reduced photosynthetic capacity leads to inefficient light use during the regrowth phase which results in lower overall TAG yields compared to a batch process.
为了实现商业可行的微藻甘油三酯（TAG）生产，需要高TAG生产率。操作策略会影响TAG生产率，但缺乏不同策略之间的系统比较。为此，在连续光照下，在实验室规模的分批培养和重复分批培养（定期收获部分培养物并重新供应富氮培养基）中研究了微拟球藻对氮饥饿和富氮培养基补充的生理反应，并将其浓缩为一个机理模型。
该模型成功描述了两种策略，用于确定分批培养和重复分批培养的潜在改进措施，并比较两种策略在优化光照下TAG产量（每摩尔供应的光合有效辐射光子产生的TAG量）方面的情况。分批培养在光照下的TAG产量，从0.12（高光强下的基础情况）到0.49 g molph（-1）（低光强且菌株改良时），重复分批培养的产量从0.07（高光强下的基础情况）到0.39 g molph（-1）（低光强且菌株改良并重复分批培养设置优化时）。基础情况产量与当前室外TAG生产的现有技术中观察到的产量一致。
对于连续光照，优化的分批培养过程在光照下的TAG产量总是高于优化的重复分批培养过程。这主要是因为重复分批培养周期始于氮饥饿细胞。它们降低的光合能力导致再生阶段的光利用效率低下，与分批培养过程相比，导致总体TAG产量较低。
