Proteomic profiling of robust acetoclastic methanogen in chrysene-altered anaerobic digestion: Global dissection of enzymes

Abstract

Methanogen is a pivotal player in pollution treatment and energy recovery, and emerging pollutants (EPs) frequently occur in methanogen-applied biotechnology such as anaerobic digestion (AD). However, the direct effect and underlying mechanism of EPs on crucial methanogen involved in its application still remain unclear. The positive effect of chrysene (CH) on semi-continuous AD of sludge and the robust methanogen was dissected in this study. The methane yield in the digester with CH (100 mg/kg dry sludge) was 62.1 mL/g VS substrate, much higher than that in the control (46.1 mL/g VS substrate). Both methane production from acetoclastic methanogenesis (AM) and the AM proportion in the methanogenic pathway were improved in CH-shaped AD. Acetoclastic consortia, especially Methanosarcina and functional profiles of AM were enriched by CH in favor of the corresponding methanogenesis. Further, based on pure cultivation exposed to CH, the methanogenic performance, biomass, survivability and activity of typical Methanosarcina (M. barkeri) were boosted. Notably, iTRAQ proteomics revealed that the manufacturing (transcription and translation), expression and biocatalytic activity of acetoclastic metalloenzymes, particularly tetrahydromethanopterin S-methyltransferase and methyl-coenzyme M reductase with cobalt/nickel-cofactor (F430 and cobalamin), and acetyl-CoA decarbonylase/synthase with cobalt/nickel-active site, of M. barkeri were upregulated significantly with fold changes in the range of 1.21–3.20 due to the CH presence. This study shed light on EPs-affecting industrially crucial methanogen at the molecular biology level during AD and had implications in the technical relevance of methanogens.