Figure 1.

Cumulative methane production from acetate by M. mazei before and after the addition of 0.5 mmol L⁻¹ of oleate: (A) cumulative methane content measured in the bottles headspace; (B) cumulative methane production mathematically adjusted. Dashed lines represent the methane production rate (mmol L⁻¹ day⁻¹) before (SlopeB) and after (SlopeA) LCFA addition. Arrow points the moment of headspace flushing and second acetate addition (↑) and LCFA addition (↓). M. mazei (DSM 2053^T) was acquired from the Deutsche Sammlung von Mikroorganismen und Zellkulturen (DSMZ, Germany) and was grown under strict anaerobic conditions as described by Stams et al. (1993) with sodium acetate as substrate at a final concentration of 20 mmol L⁻¹. Methane production was quantified over time until the mid‐exponential phase was achieved. At this point, the methane accumulated in the headspace was quantified by gas chromatography, and after was removed under sterile conditions by flushing with 80% N₂ and 20% CO₂ gas mixture. To avoid substrate limitation during the exposure to LCFA, 10 mmol L⁻¹ of acetate was added at the moment of LCFA addition. Assays were performed in duplicate and bottles were incubated in the dark at 37°C, without agitation.