Effect of N-acyl homoserine lactone on biofilm characteristics and formation in a Poly-hydroxybutyrate-hydroxyvalerate-supported solid phase denitrification system

Abstract Quorum sensing (QS) plays an important role in biofilm formation, and its involvement in biofilm formation during heterotrophic denitrification has remained underexplored. This study investigated the impact of N-acyl homoserine lactone (AHLs) on biofilm characteristics and formation in a Poly(3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV)-supported SPD system. The effects of AHLs from SPD system on biofilm formation were conducted by batch experiments. The results revealed that exogenous addition of N-(3-Oxotetradecanoyl)-L-homoserine lactone (3-oxo-C14-HSL) resulted in the highest concentration of TB-EPS, reaching 254.2 mg/L. 3-oxo-C14-HSL has a more pronounced effect on TB-PN synthesis. However, exogenous addition of 3-oxo-C12-HSL increased the negatively charged LB-EPS content, resulting in the electrostatic exclusion and reduced cell attachment capacity and a lower degree of microbial adhesion. Furthermore, the presence of exogenous 3-oxo-C14-HSL AHLs promoted the formation of tryptophan-like proteins and humic acids. The biofilm thickness and adhesion force in EPS were 47.75 uM and 4.0 uN, respectively, when adding 3-oxo-C14-HSL. Confocal laser scanning microscopy (CLSM) studies demonstrated that the 3-oxo-C14-HSL-mediated QS system enhanced the formation of bioaggregates and increased biofilm thickness in biological denitrification. These findings confirm the involvement of AHLs-mediated QS in the regulation of biofilm characteristics and formation in SPD systems. The insights gained from this study contribute to the theoretical understanding of QS and provide practical guidance for biofilm acclimation in SPD systems.