Biofilm-based photobioreactors: their design and improving productivity through efficient supply of dissolved inorganic carbon

The potential of biofilm-based photobioreactors (PBRs) for various applications has long been recognized, and various types of biofilm-based PBRs have been developed for different applications. Compared to suspension-based PBR reactors, biofilm-based systems offer several advantages, including a significantly higher biomass concentration. However, due to the immobilization of the cells, in contrast to suspension-based systems, dissolved inorganic carbon (DIC) has to be transferred into the biofilm for consumption. Thus, to ensure efficient operation of these systems under a given lighting scheme (e.g. depending on geographical location), availability of DIC should be optimized. To achieve this, the dynamics of DIC inside the various biofilm-based PBRs, as well as the operational principles of these PBRs, need to be understood. The mini-review summarizes the designs of existing biofilm-based PBRs and reviews previous studies on DIC dynamics in various biofilms. Strategies to enhance DIC availability for the immobilized cells in biofilm-based PBRs are also discussed.