High-Efficiency Flocculation of Leptosphaerulina australis J-22 to Chlorella vulgaris: Characteristics, Optimal Parameters and Mechanisms.

Fungal flocculation as an efficient technique to harvest microalgae can effectively preserve biomass and facilitate the creation of algae-fungi aggregates. In this study, the efficiency, characteristics and the optimal parameters of flocculation of Leptosphaerulina australis J-22 that isolated from a municipal wastewater treatment plant (MWWTP) were evaluated. The flocculation process and mechanisms were also analyzed through metabolomics and transcriptomics. The results showed that the flocculation efficiency of Leptosphaerulina australis J-22 was up to 97% within 2 h with the optimal flocculation parameters of 2.5 g/L mycelium pellets at 197 rpm for 9 h. It was observed that the network structure of mycelium facilitated the C. vulgaris flocculation, while the flocculating substances such as amino acids and their structural analogs, as well as metabolites with active groups secreted by fungi had no effects on the growth of C. vulgaris. The analysis of metabolomics and transcriptomics illustrated that the flocculation processes were regulated by multiple pathways such as substance synthesis, substance transport and potential changes, etc. Leptosphaerulina australis flocculated C. vulgaris with high efficiency, offered reference for developing new symbiotic bacteria-algae wastewater treatment technologies.

真菌絮凝（Fungal flocculation）作为一种高效采收微藻（microalgae）的技术，可有效保留生物质并促进藻菌聚集体的形成。本研究对从市政污水处理厂（municipal wastewater treatment plant, MWWTP）中分离得到的南方小球腔菌（Leptosphaerulina australis）J-22的絮凝效率、特性及最优絮凝参数进行了评估，并通过代谢组学（metabolomics）与转录组学（transcriptomics）分析了其絮凝过程与作用机制。结果表明，在最优絮凝参数（菌丝体小球浓度2.5 g/L、转速197 rpm、作用时长9 h）下，南方小球腔菌J-22可在2小时内实现最高可达97%的絮凝效率。研究观察到，菌丝体的网状结构可促进普通小球藻（Chlorella vulgaris，即C. vulgaris）的絮凝采收；而真菌分泌的氨基酸及其结构类似物、带有活性基团的代谢产物等絮凝物质，对普通小球藻的生长无不良影响。代谢组学与转录组学分析显示，絮凝过程受物质合成、物质转运及潜在变化等多条通路调控。南方小球腔菌可高效絮凝普通小球藻，为开发新型共生菌藻污水处理技术提供了参考依据。