Insights about fungus-microalgae symbiotic system in microalgae harvesting and wastewater treatment: A review

Microalgae can provide a wide range of adsorption groups and have remarkable effects on pollutant removal owing to the presence of extracellular polymeric substances (EPS), with polysaccharides, polysaccharides, lipids, and nucleic acids as key components. However, the problem of high-cost harvesting of microalgae has become a bottleneck limiting their industrial application, due to microalgae due to their negatively charged cell surfaces in culture and their existence in suspended systems in their natural state. Because of their simple operation, safety and efficiency, filamentous fungi assist microalgae to forming symbiotic fungus-microalgae mycelium spheres as a new, green, and environmentally friendly microalgae harvesting technique. This review describes research progress on the construction conditions, symbiotic forces, and effectiveness of wastewater treatment using fungus-microalgae symbiotic systems. The factors influencing the construction of stable fungal-microalgal symbiotic mycelial spheres with efficient harvesting efficiency in culture (temperature, pH, carbon source, rotational speed, and light intensity), and the forces involved in the symbiotic process including electrostatic interactions, van der Waals forces, and EPS interaction, are briefly outlined. Symbiotic systems of fungi and algae in different industrial wastewaters have shown good treatment of chemical oxygen demand, total nitrogen, total phosphorous, and CO2. The current challenges and future prospects of the microalgae mycelium spheres are discussed. In addition, symbiotic mycelium spheres enhance the performance of wastewater treatment compared to microalgae or fungi system alone, which solves the difficult harvesting problem of microalgae and increases the feasibility of the system for practical industrial applications.