Microalgae show great potential for wastewater treatment and nutrient recovery. However, microalgae cultivation and harvesting are affected by the low biomass concentrations which are inherent to the photoautotrophic growth process. Mixotrophic growth can be a solution as it increases microalgae biomass concentration independently from the incident light intensity. In this work, a combined respirometric-titrimetric unit was used to assess the microalgae kinetics during such mixotrophic growth conditions for Chlorella vulgaris. Based on the experimental results, a microalgae model was extended in order to gain more insight in the delicate balance between photoautotrophic and heterotrophic growth. The results suggest that during heterotrophic growth with light in absence of external inorganic carbon sources (i.e. photoheterotrophic growth), all CO₂ produced by the heterotrophic pathway is internally recycled for photoautotrophic growth. Moreover, it was shown that photoautotrophic growth is the preferential growth mechanism under mixotrophic cultivation conditions (i.e. light + inorganic carbon + organic carbon), but that high oxygen concentrations activate the heterotrophic growth pathway to avoid photorespiration. The extended microalgae model supports these findings, with good model performance for all conducted experiments.

微藻在废水处理和养分回收方面显示出巨大潜力。然而，微藻的培养和收获受到光合自养生长过程固有的低生物量浓度的影响。混合营养生长可以解决，因为它独立于入射光强度而增加了微藻生物量浓度。在这项工作中，使用组合的呼吸-滴定仪来评估寻常小球藻的混合营养生长条件下的微藻动力学。根据实验结果，扩展了微藻模型，以便在光自养和异养生长之间的微妙平衡中获得更多的见识。结果表明，在没有外部无机碳源的情况下，在有光的异养生长过程中（即光异养生长），由异养途径产生的所有CO ₂均在内部循环用于光养养生长。此外，研究表明，光合养分生长是混合营养栽培条件下的优先生长机制（即光+无机碳+有机碳），但是高氧浓度会激活异养生长途径，从而避免光呼吸。扩展的微藻模型支持了这些发现，并为所有进行的实验提供了良好的模型性能。