Exploring the Fundamental Factors Behind Algal-Bacterial Symbiosis and Their Impact on Ecological Interactions

This study focused on important factors including light intensity, light/dark cycles, and the biomass of algae/bacteria to explore the relationship between algae and bacteria, aiming to obtain the optimal performance in the algae-sludge membrane bioreactor (AS-MBR). It was found that 3000 lux was considered to be the appropriate light intensity that could improve algal biomass and nitrogen removal among the chosen light intensities. Further analysis of results indicated that a higher or lower light intensity could not simultaneously promote algal energy absorption and nitrifying bacterial activity. Moreover, the highest average growth rate of algae (0.16 mg/L d(-1)) and the removal efficiency of NH4+-N (96.4 +/- 1.5%) were both observed during the 12-h light/12-h dark cycle, respectively. Meantime, the appropriate algal proportion would mitigate membrane fouling compared with the conventional MBR. The investigation of the mechanism suggested that light intensity, light-dark cycle, and algal proportion were significantly associated with algal photosynthesis (key proteins, chromophores, and nucleic acids), the characteristics of functional bacteria, and the underlying cognition of cell-to-cell signaling between algae and bacteria, which would further influence the reactor performance.

Automated summary

This study investigated the relationship between algae and bacteria in the algae-sludge membrane bioreactor (AS-MBR) by examining the factors of light intensity, light/dark cycles, and the biomass of algae/bacteria. The study found that an appropriate light intensity of 3000 lux could improve algal biomass and nitrogen removal. It was also observed that a 12-hour light/12-hour dark cycle and an appropriate algal proportion could enhance the growth of algae and reduce membrane fouling. The results suggest that light intensity, light/dark cycles, and algal proportion are closely associated with algal photosynthesis, bacterial characteristics, and cell-to-cell signaling between algae and bacteria, all of which impact reactor performance.