Bioremediation of domestic wastewaters integrated with enhanced biodiesel production using Desmodesmus sp. mutated by atmospheric and room temperature plasma

In this work, we analyzed the biochemical changes and cultivation feasibility of microalgae Desmodesmus sp. mutated by atmospheric and room temperature plasma (ARTP) technology in mixed wastewater. The mutant strain AT151 was cultivated in different types of pretreated wastewaters for suitable pretreatment, resulting in the highest biomass content of > 354 mg/L, with a > 52% increase in lipid production in the filtered wastewater, and the difference between 0.22-mu m and 0.45-um filtration was not significant (P > 0.05). The fatty acids of AT151 indicated a majority of C-16 and C-18 at > 86%, and the monounsaturated fatty acid content exceeded 18%, which was beneficial for high-quality biodiesel. Nutrient removal was found to be visible in wastewater by cultivating mutant microalgae AT151. The removal rates of total nitrogen (TN), total phosphorus (TP), and total organic carbon (TOC) for AT151 cultivated in wastewater were more than 87%, 94% and 47%, respectively. Furthermore, the relationship between the microalgae and bacteria was studied, showing significant differences in bacterial community (P < 0.05). The obvious phenomenon consisted of dominant bacteria changes, where Brevundimonas balnearis and Synechocystis sp. served as stable strains during cultivation, forming a symbiotic relationship with mutant microalgae AT151. The dominant bacteria showed obvious metabolism according to functional KEGG prediction, mainly affecting the factors of amino acids, carbohydrates, and growth factor metabolism. Therefore, enhancing microalgae biomass and lipid production through wastewater cultivation holds both scientific significance and practical feasibility.