Lipids are energy-rich compounds. This energy can be conserved as biogas in anaerobic bioreactors but the process is frequently hindered by long-chain fatty acids (LCFA) accumulation. LCFA catabolism is thought to occur via beta-oxidation, performed by anaerobic bacteria that live in obligatory syntrophy with H2 consuming methanogens, but the initial steps of unsaturated LCFA biodegradation are still unclear. In this work we hypothesize that these initial steps do not depend on interspecies H2 transfer. To test this, six anaerobic bioreactors were continuously fed with saturated or unsaturated ...