High-efficiency flocculation of Leptosphaerulina australis J-22 to Chlorella vulgaris: Characteristics, optimal parameters and mechanisms

Abstract

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.