Effect of exogenous quorum sensing signals on biohydrogen production in an anaerobic continuous stirred tank reactor

Symbiotic relationships within the hydrogen producing microbial community play a pivotal role in sustaining the environment for optimal biohydrogen production. However, despite the significance of microbial interactions, there remains a notable research gap regarding the role of quorum sensing (QS), a cell-to-cell communication strategy that regulates group behaviors based on population density, in the biohydrogen production process. In this study, the effect of QS molecules on bio-hydrogen production in a continuous stirred tank reactor (CSTR) was examined for the first time. CSTRs with a working volume of 2.9 L were used to observe biohydrogen production. Exogenous addition of a cocktail of N-acyl homoserine lactones (AHLs) increased bio-hydrogen production during dark fermentation with the alteration of microbial community in the system. The results showed an increase in hydrogen production rate and hydrogen yield to 24.6 ± 0.4 L H₂/L-d and 2.92 ± 0.05 mol H₂/mol glucose _added, respectively, after adding AHLs into the system. Microbial community analysis revealed that the addition of AHLs increased the abundance of the Clostridium genus, known as hydrogen-producing bacteria, by 7.6–14.5 %, which appears to have played an important role in increasing hydrogen production. Therefore, this study suggests that QS signaling plays an important role in biological hydrogen production and confirms the increase of hydrogen production through its regulation.