Effect of G-C3n4 Nanoparticles Concentration on the Characteristics and Microbial Community Analysis of Algal-Bacterial Symbiosis System Under Visible Light Illumination

Abstract

Rapidly establishing and maintaining a stable algal-bacterial symbiotic system, a promising technology for wastewater treatment, presents a significant challenge. In this study, the graphitic carbon nitride nanoparticles (g-C3N4-NPs) were introduced into the system to enhance the symbiotic relationship between bacteria and algae. Results showed that the addition of 50 mg/L g-C3N4-NPs (R2 system) exhibited excellent wastewater treatment performance compared with the surplus (R3 system) or without g-C3N4-NPs (R1 system). Further investigation revealed that the chlorophyll a (Chl-a) concentration in the R2 system was 28.7% and 10.2% higher than in the R1 and R3 system, respectively. Meantime, a balanced growth between bacteria and algae was established more rapidly in R2. Moreover, R2 exhibited higher particle size and lower zeta potential absolute value. The above results suggested that the proper concentration g-C3N4-NPs may be contributed to increase the algal growth and improve the establishment of symbiotic relationship of algal-bacterial. Further mechanism investigation demonstrated that appropriate g-C3N4-NPs positively influence extracellular polymeric substance (EPS) secretion and electron transfer, thereby improving the activity, stability, and physicochemical properties of microbial aggregates and further promotes algal-bacterial interactions. Consequently, the appropriate g-C3N4-NPs inoculation increased bacterial diversity and shifted community structure. This stimulation selectively favored algal members beneficial for algal-bacterial consortia formation, potentially contributing to the enhanced performance of the algal-bacterial system.

Keywords: g-C3N4 nanoparticles, Algal-bacterial system, Extracellular polymeric substance, Microbial enzymatic activity, Microbial community analysis.