Microalgal–Bacterial Synergistic Interactions and Their Potential Influence in Wastewater Treatment: a Review

Microalgae, as the most promising raw material for biodiesel, can absorb and transform N, P, and organic matter in wastewater into cell components such as oil, carbohydrate, and protein. The cultivation of microalgae in wastewater provides the possibility to realize harmless treatment and resource utilization of wastewater and reduce the cost of microalgal culture. Whether in a single microalgal culture process or wastewater system, there always be a large number of bacteria interacting with microalgae, forming a complex microecological system. Although microalgal–bacterial coculture system is feasible features for the higher biomass production and better nutrient adaptability from wastewater, the precise understanding of interaction and coexistence in water bodies is still unclear. Some major challenges are to develop sustainability in the microalgal–bacterial coculture system due to the incomplete knowledge about the mechanism of communication, algal growth promotion, and effect of microalgae on the indigenous bacteria in wastewater. In the present review, nutritional interaction and signal transduction, two main interaction models of algae and bacteria, and the effect of synergism of these two models on microalgal system are summarized. Moreover, the impact of algal–bacterial coculture on algal growth and removal of pollutants in wastewater treatment process was expounded systematically to develop highly efficient consortium systems by covering the sustainability limitations. This work would provide guidance for the establishment of efficient algal–bacterial symbiosis system in the wastewater with complex microecology and nutrient environment to improve the accumulation of microalgal biomass and reduce the cost of microalgal culture.