Enhancing mixed-species microalgal biofilms for wastewater treatment: Design, construction, evaluation and optimisation

Biofilm-based cultivation of microalgae is a powerful method for wastewater treatment with low harvesting costs, water and energy consumption. This article provides a detailed summary of the design, construction, evaluation, and optimisation (DCEO) of mixed-species biofilms including algal and bacteria, and discusses their relevant applications in the treatment of industrial and agricultural wastewater and new pollutants. Finally, it presents the problems faced by mixed-species microalgal biofilms, along with solutions. DCEO is a typical synthetic biology concept, in which design and construction are bottom-up, and evaluation and optimisation are top-down approaches. Detailed knowledge of the metabolic pathways and the regulation of microalgae and other microorganisms is helpful for designing mixed-species biofilms. Three dimensional bioprinting is a powerful tool for constructing structured biofilms. Further analysis after evaluation is beneficial to optimise such biofilms. This review provides a new insight into using DCEO to enhance mixed-species biofilms for wastewater treatment.