Metagenomic insight of fluorene-boosted sludge acidogenic fermentation: Metabolic transformation of amino acids and monosaccharides

Fluorene (Flu) occurs widely in various environments and its toxicity to organisms is well-known. However, the impact of Flu on complicated biochemical processes involving functional microbial community has been reported rarely. In this study, the facilitation of Flu on the volatile fatty acids (VFAs) generation executed by acidogenic microbial population during sludge acidogenic fermentation (37 degrees C, SRT = 8 d, pH = 10.0) was investigated. The accumulation of VFAs (particularly acetic acid) increased initially and then declined with the increasing of Flu concentration (0-500 mg/kg dry sludge), which reached a maximum (3211.1 mg COD/L) as Flu content was 200 mg/kg dry sludge. The Fluenhanced VFAs production was primarily attributed to the shift of hydrolysis/acidification, as well as the corresponding functional microbial community and the activity of enzymes. Based on the metagenomics analysis, the conversion of organic substrates, i.e. amino acid and monosaccharide, into VFAs embraced in hydrolysis/acidification shaped by Flu was constructed at the genetic level. The relative abundances of genes included in aminotransfer and deamination process of amino acid and glycolysis of monosaccharide into VFA-precursors (pyruvate, acetyl-CoA and propionyl-CoA), and the further formation of VFAs were improved due to the Flu presence. This study shed light on the Flu-affected microbial processes at the molecular biology level during acidogenic fermentation and was of great significance in resource recovery of sludge containing persistent organic pollutants.

Automated summary

This study investigated the facilitation of Fluorene (Flu) on volatile fatty acids (VFAs) generation during sludge acidogenic fermentation. The results showed that the accumulation of VFAs, especially acetic acid, increased with the addition of Flu, reaching a maximum at a concentration of 200 mg/kg dry sludge. Metagenomics analysis revealed that Flu altered the hydrolysis/acidification process, promoting the conversion of amino acids and monosaccharides into VFAs. This study provides insights into the molecular biology level processes affected by Flu during acidogenic fermentation and is significant for resource recovery of sludge containing persistent organic pollutants.