Feeding regime selectively enriching acetoclastic methanogens to enhance energy production in anaerobic digestion systems

Abstract

Applying the r/K selection theory to explore the distribution patterns of acetoclastic methanogens under varying conditions is rare, although it can offer a basis for optimizing community structure and enhancing methane production in anaerobic digestion systems. Different operating modes (sequencing batch reactors, SBRs; and continuous-flow reactors, CFRs) and solids retention times (SRTs; 15 and 50 days) were adopted to acclimate different acetoclastic methanogens in acetate-fed anaerobic reactors. SBRs exhibited a significantly higher CH₄ production rate than CFRs (P = 0.037). Methanosarcina exhibited a higher relative abundance in SBRs (13.7 ∼ 16.1 %) than in CFRs (0.2 ∼ 0.3 %), aligning with its typical r-strategist characteristics. Methanothrix showed a higher enrichment in CFRs (33.1 ∼ 39.6 %) compared to SBRs (26.8 ∼ 29.9 %) at the same SRT, indicating K-strategist behavior. The SBRs had the potential to co-enrich both types of methanogens. Feeding regimes played a more pivotal role in the distribution of methanogens than SRT. The dominant bacteria, such as Desulfococcus and Mesotoga, as well as the archaeon Methanothrix, were auxotrophic in some essential amino acids, implying potential cross-feeding interactions. This study provides key insights into ecological strategies by linking microbiology with environmental technologies to enrich target methanogenic communities and enhance methane production.