1 research outputs found
Conversion of C<sub>n</sub>‑Unsaturated into C<sub>n‑2</sub>-Saturated LCFA Can Occur Uncoupled from Methanogenesis in Anaerobic Bioreactors
Fat, oils, and grease present in
complex wastewater can be readily
converted to methane, but the energy potential of these compounds
is not always recyclable, due to incomplete degradation of long chain
fatty acids (LCFA) released during lipids hydrolysis. Oleate (C18:1)
is generally the dominant LCFA in lipid-containing wastewater, and
its conversion in anaerobic bioreactors results in palmitate (C16:0)
accumulation. The reason why oleate is continuously converted to palmitate
without further degradation via β-oxidation is still unknown.
In this work, the influence of methanogenic activity in the initial
conversion steps of unsaturated LCFA was studied in 10 bioreactors
continuously operated with saturated or unsaturated C16- and C18-LCFA,
in the presence or absence of the methanogenic inhibitor bromoethanesulfonate
(BrES). Saturated C<sub>n‑2</sub>-LCFA accumulated both in the presence
and absence of BrES during the degradation of unsaturated C<sub>n</sub>-LCFA, and represented more than 50% of total LCFA. In the presence
of BrES further conversion of saturated intermediates did not proceed,
not even when prolonged batch incubation was applied. As the initial
steps of unsaturated LCFA degradation proceed uncoupled from methanogenesis,
accumulation of saturated LCFA can be expected. Analysis of the active
microbial communities suggests a role for facultative anaerobic bacteria
in the initial steps of unsaturated LCFA biodegradation. Understanding
this role is now imperative to optimize methane production from LCFA