Microalgae are widely be used in carbon sequestration, food supplements, natural pigments, polyunsaturated fatty acids, biofuel applications, and wastewater treatment. However, the difficulties incurred in algae cell separation and harvesting, and the exorbitant cost required to overcome these challenges, are the primary limitations to large-scale industrial application of microalgae technology. Herein, we explore the potential of inducing flocculation by adjusting the pH for pre-concentrating Euglena gracilis. Our results demonstrate that flocculation can be induced by increasing the medium pH to 8.5; however, most of the algae cells were broken by increasing the pH > 10. Magnesium phosphate, calcium phosphate, and their derivatives precipitation jointly led to flocculation, although calcium phosphate and its derivatives precipitation had a greater effect. This study demonstrates that pH treatment-induced flocculation is efficient and feasible for the pre-concentration of E. gracilis under a pilot-scale culture system. Moreover, it also maintained the microalgae cells’ integrity, chlorophyll production, and increased paramylon production. These findings provide a theoretical basis for reducing the cost of large-scale E. gracilis harvesting; as well as provide a reference for harvesting other microalgae.

中文翻译：

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通过弱碱性pH处理预浓缩微藻Euglena gracilis以及Ca3(PO4)2、Mg3(PO4)2及其衍生物的絮凝机理。


微藻广泛用于碳封存、食品补充剂、天然色素、多不饱和脂肪酸、生物燃料应用和废水处理。然而，藻类细胞分离和收获的困难以及克服这些挑战所需的高昂成本是微藻技术大规模工业应用的主要限制。在此，我们探索通过调节预浓缩细小裸藻的 pH 值来诱导絮凝的潜力。我们的结果表明，通过将介质 pH 值提高到 8.5 可以诱导絮凝；然而，当pH>10时，大多数藻细胞被破坏。磷酸镁、磷酸钙及其衍生物沉淀共同导致絮凝，但磷酸钙及其衍生物沉淀效果更大。本研究表明，pH 处理诱导的絮凝对于在中试规模培养系统下预浓缩 E. gracilis 是有效且可行的。此外，它还保持了微藻细胞的完整性、叶绿素的产生，并增加了裸藻淀粉的产生。这些研究结果为降低大规模E. gracilis收获成本提供了理论依据；也为其他微藻的收获提供参考。