State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
YANGTZE Eco-Environment Engineering Research Center, China Three Gorges Corporation, Wuhan 430010, China; National Engineering Research Center of Eco-environment Protection for Yangtze River Economic Belt, China Three Gorges Corporation, Wuhan 430010, China.
Water Res. 2024 Oct 15;264:122172. doi: 10.1016/j.watres.2024.122172. Epub 2024 Jul 31.
Cultivation of microalgae using anaerobic digestate is a gain-win strategy for algal biomass production and achieving environmental benefits. However, the low biomass concentration and high harvest cost of the conventional suspended microalgae culture system are troublesome issues. In this study, a novel fluidized bed photobioreactor (FBPBR) based on diatomite powder was constructed for cultivating Scenedesmus quadricauda and treating diluted anaerobic digestate. The optimized diatomite carrier dosage of 750 mg/L increased microalgal biomass concentration to 1.58 g/L compared to suspended microalgae without carrier (0.99 g/L). When the light intensity was increased from 100 to 200 μmol/m/s, the microalgal biomass in the FBPBR increased to 1.84 g/L and the settling efficiency increased to 93.58 %. This was due to the 1.60-fold enhancement of extracellular polymeric substance (EPS) secretion and changes in EPS properties. The increase in hydrophobic functional groups of EPS under high light intensity, coupled with the reconstitution of protein secondary structure, facilitated the initial attachment of algae to diatomite and the thickening of microalgal biofilm. Moreover, transcriptomic analysis demonstrated that diatomite promoted antioxidant defense and photosynthesis in S. quadricauda cells, alleviating the adverse effect of anaerobic digestate stress. The diatomite addition and elevated light intensity contributed to the highest lipid content (60.37 %), which was owing to the upregulated genes encoding fatty acid and triacylglycerol synthesis under the stress of localized nutrient starvation in the inner layer of microalgae biofilms. Furthermore, the regulation of phosphorus metabolism and NH-N assimilation improved nutrient removal (93.24 % and 96.86 % for NH-N and TP removal). This work will provide guidance for the development of FBPBR based on diatomite powder.
利用厌氧消化液培养微藻是一种获得双赢的策略，既能生产藻类生物质，又能带来环境效益。然而，传统悬浮微藻培养系统的生物量浓度低和高收获成本是令人困扰的问题。在这项研究中，构建了一种基于硅藻土粉末的新型流化床光生物反应器（FBPBR），用于培养四尾栅藻和处理稀释的厌氧消化液。与无载体的悬浮微藻（0.99 g/L）相比，优化的硅藻土载体用量 750 mg/L 将微藻生物量浓度提高到 1.58 g/L。当光照强度从 100 μmol/m/s 增加到 200 μmol/m/s 时，FBPBR 中的微藻生物量增加到 1.84 g/L，沉降效率增加到 93.58%。这是由于细胞外聚合物（EPS）分泌增加了 1.60 倍，并且 EPS 性质发生了变化。高光强下 EPS 中疏水性官能团的增加，加上蛋白质二级结构的重建，促进了藻类对硅藻土的初始附着和微藻生物膜的增厚。此外，转录组分析表明，硅藻土促进了 S. quadricauda 细胞的抗氧化防御和光合作用，缓解了厌氧消化液胁迫的不利影响。硅藻土的添加和光照强度的提高导致了最高的脂质含量（60.37%），这是由于在微藻生物膜内层局部营养饥饿的胁迫下，编码脂肪酸和三酰基甘油合成的基因上调。此外，磷代谢和 NH-N 同化的调节提高了营养物质的去除率（NH-N 和 TP 的去除率分别为 93.24%和 96.86%）。这项工作将为基于硅藻土粉末的 FBPBR 的开发提供指导。
