Quorum sensing signals enhanced caproate production by changing microbial community in chain elongation enrichments

Abstract Quorum sensing (QS) has been widely used to regulate the cell-cell communication. N-acyl-homoserine lactones (AHLs) are typical small-molecule mediating QS among intraspecific communication. In this study, AHLs were investigated to enhance the production of caproate from ethanol and acetate in chain elongation enrichments. N-hexanoyl- L -homoserine lactone (C6-HSL), N-octanoyl- L -homoserine lactone (C8-HSL), and N-(3-oxodecanoyl)- L -homoserine lactone (3OC10- HSL) were added as the signal molecule. Results showed that the highest caproate concentration, 8.46 g/L, was obtained with the addition of C8-HSL (35.14% higher than the control) when ethanol and acetate were substrate. These reinforcement effect of AHLs may be related to enhance content of protein (C8-HSL increased by 466.00 mg/L as relative to the control group) and total biomass (1.99 times of the control group with the addition of C8-HSL). Moreover, the relative abundance of Negativicutes and the concentration of acetyl-CoA were increased, and function prediction of bacterial community suggested that the relative abundance of acetyl-CoA acetyltransferase was improved obviously, which indicated microbial community of chain elongation were more active in presence of AHLs. This study provides an insight to the biotechnology application of chain elongation for caproate production.