Carrier with cyclodextrin and quorum sensing synergy: An efficient method for selective enrichment of anammox bacteria.

[Display omitted] • A novel biofilm carrier with quorum sensing regulatory ability was constructed. • The novel carrier prompts granular sludge-like biofilm formation. • The novel carrier enriched anammox bacteria (AnAOB) at 3.2 times the original speed. • A new ability of cyclodextrin to enrich difficult-to-culture bacteria was discovered. • Exogenous quorum sensing signaling molecules can reconstruct AnAOB dominant species. High-efficiency enrichment of functional bacteria is one of the biggest technical barriers to the application of anaerobic ammonium oxidation (anammox). This study combined biofilm carriers and quorum sensing to achieve rapid biomass accumulation. A biofilm carrier with biomass adsorption and quorum sensing regulation functions was developed for the rapid start-up of the reactor and enrichment of anammox bacteria (AnAOB). The nitrogen removal rates of the three reactors were further tested, and the carrier mechanism was explored. The start-up time of the reactor with the modified carriers was 28 days, which was ∼44 % shorter than that of the reactor without carriers. After 90 days of operation, the absolute abundance of total AnAOB was 3.2 times that in the control group. The modified carrier promoted the rapid adhesion of biomass through the hydrophobic cavity of cyclodextrin and induced rapid proliferation, enhancement of activity, and extracellular protein secretion of AnAOB through quorum sensing signaling molecules. Finally, a special hydrophobic biofilm with granular sludge characteristics was formed on the modified carrier through the self-assembly of hydrophobic biomass particles. Overall, we propose a novel approach to enrich anammox bacteria involving a combination of quorum sensing and biofilm carriers. [ABSTRACT FROM AUTHOR]