Algal–bacterial consortia for bioproduct generation and wastewater treatment

Microalgae have been developed as promising candidates for bioenergy production, coupled with answering challenges related to water pollution and global warming. When combined with wastewater, microalgal biomass production could be freed from a strong dependence on freshwater and chemical nutrients, as well as achieve the additional advantage of wastewater reclamation. However, despite those dual benefits, certain limitations on the growing of algae in wastewater remain to be resolved, including the inevitable presence of bacteria in wastewater, which influences biomass productivity and quality in various ways. Pointing at microalgal-bacterial relationships, this study provides an updated review of the application of microalgal-bacterial consortia (MABC) to benefit biomass yield and harvest, and in wastewater remediation, focusing on the main interactions established between the microorganisms integrated within MABC and the factors influencing the behaviours of MABC. The challenges faced by the MABC biotechnology are also discussed, which are primarily rooted in undesirable bacteria that parasitically eat microalgal products and inhibit algal growth through nutrient competition, lysate exudation, or reducing the algal resistance to biotic stress. However, there is a lack of systematic studies on maintaining stable and effective operation of MABCs for wastewater cultivation and high-value bioproduct generation. Knowledge gaps are identified as including systematic information about the responses of MABC to culture conditions and wastewater-borne bacterial communities, and the metabolic mechanisms underpinning the interactions between algae and bacteria in wastewater. Further research focuses and methodologies are proposed in this review, making full use of the advent of omics and computational technology.