Algal-bacterial symbiosis strengthens the treatment of high-salinity phenolic wastewater and its molecular mechanism

Abstract

This study developed algal-bacterial symbiotic flocs (ABSF) for high-salinity phenolic wastewater treatment, showcasing superior performance over activated sludge (AS). ABSF exhibited exceptional structural stability, producing 417.64 mg g⁻¹ extracellular polymeric substances (EPS) and accumulating 51.2 % lipids. It achieved complete phenol removal and significantly reduced effluent total nitrogen (9.36 vs. 23.59 mg L⁻¹ in AS) and COD (77.76 vs. 105.34 mg L⁻¹), maintaining efficiency even at a 1-day hydraulic retention time. Metagenomic analysis revealed ABSF's diverse microbial community, enriched with functional genera (Candidatus Nitrosocosmicus, Synechocystis, Thauera) linked to nitrogen and aromatic degradation. Enhanced quorum sensing was evidenced by elevated N-acyl-homoserine lactones (C6-HSL: 38.56 ng mL⁻¹) and upregulated signal transduction genes (5.4 % abundance). ABSF also showed higher expression of phenol-degrading enzymes and metabolic genes (e.g., succinate dehydrogenase: 0.19 %), accelerating the TCA cycle for efficient pollutant mineralization. Key mechanisms included EPS-mediated stress resistance, microbial synergy, and robust metabolic activity. These findings highlight ABSF as a sustainable solution for refractory industrial wastewater, combining high treatment efficiency with resource recovery potential, offering both environmental and economic benefits.

Keywords: Algal-bacterial symbiotic flocs; Metagenomics; Molecular mechanism; Phenol degradation; Signaling molecules.