Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University, Graaf Karel de Goedelaan 5, B-8500 Kortrijk, Belgium.
Laboratory for Industrial Water and Ecotechnology (LIWET), Department of Green Chemistry and Technology, Ghent University, Graaf Karel de Goedelaan 5, B-8500 Kortrijk, Belgium.
Sci Total Environ. 2021 Aug 25;784:147048. doi: 10.1016/j.scitotenv.2021.147048. Epub 2021 Apr 15.
With the emerging need of nutrient recycling in resource recovery facilities, the use of microalgae-bacteria flocs has received considerable attention in the past few years. However, although the main biological processes are already known, the complex interactions occurring between algae and bacteria are not fully understood. In this work, a combined respirometric-titrimetric unit was used to assess the microorganisms' kinetics within microalgae-bacteria flocs under different growth regimes (i.e. photoautotrophic, heterotrophic and mixotrophic) and different ratios of inorganic (IC) to organic carbon (OC) (IC:OC-ratios). Using this respirometric-titrimetric data, a new model was developed, calibrated and successfully validated. The model takes into account the heterotrophic growth of bacteria, the photoautotrophic, heterotrophic and mixotrophic growth of algae and the production and consumption of extracellular polymeric substances (EPS) by both bacteria and algae. As such, the model can be used for detailed analysis of the carbon fluxes within microalgae-bacteria flocs in an efficient way. Model analysis revealed the high importance of the EPS regulatory mechanism. Firstly, under heterotrophic growth conditions, OC-uptake occurred during the first 10-15 min. This was linked with internal OC storage (49% of added OC) and EPS production (40%), as such providing carbon reserves which can be consumed during famine conditions. Moreover, the algae were able to compete with bacteria for OC. Secondly, under photoautotrophic conditions, algae used the added IC to grow (57% of added IC) and to produce EPS (29%), which consecutively stimulated heterotrophic bacteria growth (20%). Finally, under mixotrophic conditions, low IC:OC-ratios resulted in an extensive OC-storage and EPS production (50% of added C) and an enhanced microalgal CO reuse, resulting in an increased algal growth of up to 29%.
随着资源回收设施中营养物质回收需求的出现，微藻-细菌絮体的应用在过去几年中受到了相当多的关注。然而，尽管主要的生物过程已经为人所知，但藻类和细菌之间发生的复杂相互作用仍未被完全理解。在这项工作中，使用组合呼吸计-滴定单元来评估不同生长阶段（即自养、异养和混合营养）和不同无机碳（IC）与有机碳（OC）比（IC:OC 比）下微藻-细菌絮体中微生物的动力学。使用这种呼吸计-滴定数据，开发、校准并成功验证了一个新模型。该模型考虑了细菌的异养生长、藻类的自养、异养和混合营养生长以及细菌和藻类产生和消耗细胞外聚合物物质（EPS）。因此，该模型可以有效地用于分析微藻-细菌絮体中的碳通量。模型分析揭示了 EPS 调节机制的高度重要性。首先，在异养生长条件下，OC 在最初的 10-15 分钟内被吸收。这与内部 OC 储存（添加 OC 的 49%）和 EPS 生产（40%）有关，从而提供了可以在饥荒条件下消耗的碳储备。此外，藻类能够与细菌竞争 OC。其次，在自养条件下，藻类利用添加的 IC 生长（添加 IC 的 57%）和产生 EPS（29%），这继而刺激了异养细菌的生长（20%）。最后，在混合营养条件下，低 IC:OC 比导致大量 OC 储存和 EPS 生产（添加 C 的 50%）以及增强的微藻 CO 再利用，导致藻类生长增加了 29%。
