Impact of 5-Fluorouracil on Anaerobic Digestion Using Sewage Sludge

Abstract

The role of bacterial interaction is important for controlling bacterial functions; however, it has been not fully understood in microbial consortia (such as anaerobic digestion). In this study, fluorouracil (FU), which is not only an anticancer agent but also a quorum sensing (QS) inhibitor to some of the Gram-negative bacteria, was found to inhibit methane production from sewage sludge under an anaerobic condition as shown in a result that methane production in the presence of FU was 8 times lower than the control (sewage sludge without FU). Whereas FU did not influence the process of hydrolysis, in the acidogenesis/acetogenesis process, butyrate and acetate accumulated in samples with FU. Also, in the methanogenesis process, FU remarkably inhibited methane production by acetoclastic methanogens rather than that by hydrogenotrophic ones. The result was in agreement with a result that growth and methane production of Methanosarcina acetivorans C2A were inhibited in the presence of FU. However, the inhibitory effect by FU was high in a condition that both the bacteria and archaea are active. It indicates that FU influences not only methanogens but also bacteria in the process of methane fermentation. The analyses of microbial communities (bacteria and archaea) showed that the abundance ratio of the Firmicutes phyla is high and hydrogenotrophic methanogens become dominant in the presence of FU. On the other hand, the abundance of Spirochaetes significantly decreased under FU. The inhibition of methane production by FU was not only due to the growth inhibition of methanogenic archaea, but also due to the changes in the composition of the bacterial population.

Keywords: Anaerobic digestion, sewage sludge, fluorouracil, methane production, pollutant