Posted by 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.
A ceramic carrier substrate with a polyurethane sponge structure was developed in this study to improve adhesion. 3-aminopropyl triethoxysilane (KH550) was used to modify the porous ceramics for the subsequent introduction of AHLs. Carboxymethyl β-CD was grafted onto the modified carrier obtained in the previous step for the encapsulation and sustained release of alkylhomoserine lactones (AHLs) signaling molecules.
The novel biofilm carrier developed has the ability to release quorum-sensing signaling molecules that benefit AnAOB and efficiently enriched AnAOB at 3.2 times the speed achieved without carrier and significantly shortened the reactor start-up time. Surprisingly, the efficacy analysis revealed that cyclodextrin has significant potential for rapid biofilm formation. Cyclodextrin performs in multiple roles throughout the biofilm formation process, ultimately resulting in the formation of previously unreported particulate biofilms.
Rapid enrichment of difficult-to-culture microorganisms has long been a challenging issue, and cyclodextrin seems to provide a new solution.