Correlation of extracellular polymeric substances and microbial community structure in denitrification biofilm exposed to adverse conditions

Abstract

Microbial community may respond to different adverse conditions and result in the variation of extracellular polymeric substances (EPS) in denitrification biofilm; this study discovered the role of EPS in accordance with the analysis of cyclic diguanylate (c-di-GMP) and electron equilibrium (EE) under low organic loading rate, shock organic loading rate and low temperature conditions. Good nitrate removal performance could be achieved under shock organic loading rate and low temperature conditions; however, owing to the low organic loading rate, the carbon source was preferentially utilized for biomass growth. Tightly bound EPS (TB-EPS) contents progressively increased and facilitated cell adhesion and biofilm formation. The stable TB protein (TB-PN) content in TB-EPS built a cross-linked network to maintain internal biofilm structure and led to the rapid biosynthesis of polysaccharides, which could further enhance microbial adhesion and improve nitrate removal. C-di-GMP played an important role in biomass retention and biofilm formation, based on the correlation analysis of c-di-GMP and EPS. TB polysaccharide (TB-PS) contents presented a significant positive correlation with c-di-GMP content, microbial adhesion and biofilm stabilization was further enhanced through c-di-GMP regulation. In addition, a remarkable negative correlation between electron deletion rate (EDR) and TB-PN and TB-PS was discovered, and TB-PS was required to serve as energy source to enhance denitrification according to EE analysis. Surprisingly, dynamic microbial community was observed due to the drastic community succession under low temperature conditions, and the discrepancy between the dominant species for denitrification was found under shock organic loading rate and low temperature conditions. The notable increase in bacterial strains Simlicispira, Pseudomonas and Chryseobacterium was conducive to biofilm formation and denitrification under shock organic loading rate, while Dechloromonas and Zoogloea dramatically enriched for nitrate removal under low temperature conditions. The high abundance of Dechloromonas improved the secretion of EPS through the downstream signal transduction, and the c-di-GMP conserved in Pseudomonas concurrently facilitated to enhance exopolysaccharide production to shock organic loading rate and low temperature conditions.

pH-Dependent Hydrogenotrophic Denitratation Based on Self-Alkalization

“…Given that the only MAG possessing hydrogenase genes was co.bin.3, there must be alternate electron donors directly or indirectly derived from hydrogen oxidation, which could support other nonhydrogenotrophic members in the community. Carbon substances including polyhydroxybutyrate (PHB) and extracellular polymeric substances (EPS) are conceivable alternatives, as they are able to maintain microbial nitrate reduction. , However, batch tests without H 2 addition showed no nitrate being reduced (Figure S4), excluding the possibility of PHB/EPS accumulation and consumption and the use of dissolved carbon in the liquid. How these nonhydrogenotrophic members obtained electrons warrants further research.…”

“…Carbon substances including polyhydroxybutyrate (PHB) and extracellular polymeric substances (EPS) are conceivable alternatives, as they are able to maintain microbial nitrate reduction. 52,53 However, batch tests without H 2 addition showed no nitrate being reduced (Figure S4), excluding the possibility of PHB/EPS accumulation and consumption and the use of dissolved carbon in the liquid. How these nonhydrogenotrophic members obtained electrons warrants further research.…”

Diagnostic Method for Enhancing Nitrogen and Phosphorus Removal in Cyclic Activated Sludge Technology (CAST) Process Wastewater Treatment Plant

“…As depicted in Figure 5, the highest concentration of influent ammonia nitrogen is about 31.0 mg/L, the lowest value is 12.5 mg/L, and the average value is approximately 20.7 mg/L. The peak value of effluent ammonia nitrogen concentration appears in winter likely due to the low bioactivity of activated sludge [7], but the effluent ammonia nitrogen concentration is still greater than the discharge standard. In addition, the effluent ammonia nitrogen was less than 3.0 mg/L with the increase in temperature.…”

“…The denitrification reaction is a process in which denitrifying bacteria reduce nitrite and nitrate to gaseous nitrogen (N 2 ) under anoxic conditions [7]. Denitrification rate, denitrification potential, and the endogenous denitrification rate were measured to investigate the denitrification performance of activated sludge in the CAST process.…”