Effect of sulfate on methanogenic communities that degrade unsaturated and saturated long‐chain fatty acids (LCFA)

Abstract

Anaerobic bacteria involved in the degradation of long-chain fatty acids (LCFA), in the presence of sulfate as electron acceptor, were studied by combined cultivation-dependent and molecular techniques. The bacterial diversity in four mesophilic sulfate-reducing enrichment cultures, growing on oleate (C(18:1), unsaturated LCFA) or palmitate (C(16:0), saturated LCFA), was studied by denaturing gradient gel electrophoresis (DGGE) profiling of polymerase chain reaction (PCR)-amplified 16S rRNA gene fragments. These enrichment cultures were started using methanogenic inocula in order to assess the competition between methanogenic communities and sulfate-reducing bacteria. Phylogenetic affiliation of rRNA gene sequences corresponding to predominant DGGE bands demonstrated that members of the Syntrophomonadaceae, together with sulfate reducers mainly belonging to the Desulfovibrionales and Syntrophobacteraceae groups, were present in the sulfate-reducing enrichment cultures. Subculturing of LCFA-degrading methanogenic cultures in the presence of sulfate resulted in the inhibition of methanogenesis and, after several transfers, archaea could no longer be detected by real-time PCR. Competition for hydrogen and acetate was therefore won by sulfate reducers, but acetogenic syntrophic bacteria were the only known LCFA-degrading organisms present after subculturing with sulfate. Principal component analysis of the DGGE profiles from methanogenic and sulfate-reducing oleate- and palmitate-enrichment cultures showed a greater influence of the substrate than the presence or absence of sulfate, indicating that the bacterial communities degrading LCFA in the absence/presence of sulfate are rather stable.

Effect of COD:SO4 2− Ratio, HRT and Linoleic Acid Concentration on Mesophilic Sulfate Reduction: Reactor Performance and Microbial Population Dynamics

“…This relationship could enhance the SO4 2− reduction in the process as short chain fatty acids such as propionate, butyrate could be degraded to acetate which is a more preferred carbon substrate for SRBs in comparison to propionate and butyrate [15]. Studies by Sousa et al [20] also suggest that these syntrophic bacteria existed along with SRBs in LCFA degrading communities in the presence of SO4 2− .…”

“…were abundant (Supplementary Table S1). According to Sousa et al [20] and Tan et al [38], these microorganisms were detected in SO4 Table S1). The presence of Clostridium sp.…”

“…Inhibiting MPAs by utilizing chemical inhibitors could be of great significance in reducing methanogenesis by diverting electron fluxes to SRBs and subsequently improve SO4 2− removal. Inhibiting methanogens with long chain fatty acids (LCFAs) have gained some attention over other inhibitory chemicals [19] because they are environmentally friendly, relatively abundant and biodegradable [20].…”

Diversity of Five Anaerobic Toluene-Degrading Microbial Communities Investigated Using Stable Isotope Probing

“…Members of Syntrophobacteraceae were previously identified as sulfate-reducing bacteria (17,37) and can degrade long-chain fatty acids (54,55) and propionate (6) under sulfate-reducing conditions. The closest relative of the sequences represented by the 204-bp TRF with a validly published name is Syntrophobacter wolinii (18), sharing 91% sequence similarity.…”

Microbial Community Composition and Dynamics of Moving Bed Biofilm Reactor Systems Treating Municipal Sewage

“…In addition to domestic wastewater, the MP plant receives industrial waste from an abattoir, expected to carry large amounts of fats, oils, and greases (28). The presence of long-chain fatty acids (LCFA) derived from the degradation of lipids (45) and low water temperatures have been shown to select for SRBs in a wastewater treatment system (9,22). Enhanced SRB activity would also require access to excess sulfate as an electron acceptor.…”