Diversity of Eukaryotic Algae in Propylene Oxide Saponification Wastewater Activated Sludge

Eukaryotic algae play an important role to maintain the energy cycle and provide oxygen in the ecosystem of water environment, such as rivers, lakes, and wastewater activated sludge. As one of the important microorganisms in the activated sludge, the community structure of eukaryotic algae in the activated sludge is still not clear. Activated sludge process had been successfully used to dispose the propylene oxide (PO) saponification wastewater, which was contaminated with high chemical oxygen demand (1200–1500 mg/L) and high chlorine concentration (22000–26,000 mg/L). In this study, we focused on the diversity of eukaryotic algae in the PO saponification wastewater and municipal wastewater treatment plant. Based on Illumina Miseq high-throughput sequencing, the algae could be divided into nine different groups for the municipal wastewater activated sludge. By contrast, the algae in the PO saponification wastewater activated sludge could be grouped into two unidentified groups, which were quite different from the municipal sludge. In order to further analyze the diversity of eukaryotic algae in the PO saponification wastewater activated sludge, 18S rDNA clone library of eukaryotic algae was constructed, and 31 clones were obtained. On account of BLASTn analysis, one of them was identified as Desmodesmus intermedius, while others were considered as uncultured eukaryotic algae. Moreover, D. intermedius, which had the potential biodiesel-producing capacity, was successfully isolated from the PO saponification wastewater activated sludge. This study would open an avenue to understand the eukaryotic alage diversity and utilize the biodiesel-producing eukaryotic alage in the PO saponification wastewater activated sludge.