Synergism and mutualistic interactions between microalgae and fungi in fungi-microalgae symbiotic system

The method of collecting microalgae using fungal mycelium pellets has attracted widespread attention because of its high efficiency and simplicity. In this study, the interaction in FMSS was explored using Aspergillus fumigatus and Synechocystis sp. PCC6803. Under the conditions of 25-30 °C, pH of 5.0, 160 rpm, a light intensity of 1000 lx, light to darkness ratio of 6:18 h, and glucose concentration of 1.5 g/L, the FMSS had the highest biomass and recovery efficiency. SEM, TEM, and Zeta analysis showed that microalgae can be fixed on the surface of fungal mycelium pellets by the electrostatic attraction (amino, amide, phosphate, hydroxyl, and aldehyde groups) of EPS. The N cycling and CO2-O2 cycling promoted the synthesis of amino acids and provided a guarantee for gas exchange, and the intermediate metabolites (CO32- and HCO3-/H2CO3) satisfied the metabolic activities. The microalgae and fungi worked in coordination each other, which was the mutualistic symbiosis.