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<p>Introducing a synthetic H<sub>2</sub>/CO<sub>2</sub> gas mixture into anaerobic systems is a promising strategy for C1 gas valorization, renewable energy storage, and sustainable chemical synthesis. However, systematic comparisons of inoculum sources under identical operational conditions remain limited. In this study, three inoculum sources, fermentation sludge (S1), lake sediment (S2), and brewery anaerobic sludge (S3), were compared for acetate production from CO<sub>2</sub> and H<sub>2</sub>, with particular attention to microbial community succession and reactor stability. S3 showed the highest CO<sub>2</sub> consumption rate (331 ± 4&#xa0;mg CO<sub>2</sub>/(L·d)), cumulative CO<sub>2</sub> fixation (7.8 ± 0.3&#xa0;g/L), and acetate production efficiency (5.3% electron allocation to acetate), along with stable pH conditions (7.1 ± 0.3). These outcomes were associated with the rapid enrichment of genera that include known homoacetogenic species, mainly <i>Clostridium</i> and <i>Acetobacterium</i>, which together reached approximately 40% relative abundance in S3 after acclimation. The findings suggest that initial inoculum composition can influence the extent of homoacetogen enrichment and subsequent acetate production performance. In addition, the post-peak increase in the acetate-oxidizing genus <i>Geobacter</i> (an acetate consumer rather than an acetogen) in S3 points to a potential challenge for sustained product recovery in mixed-culture systems. Overall, these results provide insights for inoculum selection and process optimization in H<sub>2</sub>/CO<sub>2</sub> fermentation systems for acetate production.</p>

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Comparison of three inoculum sources for acetate production and microbial succession in H2/CO2-fed anaerobic system

  • 期刊论文

  • 发表日期：

    2026年7月2日

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  • Nana Jiang,
  • Linxiao Li,
  • Xiyan Li,
  • Ruixiang Li,
  • Guoliang Wang,
  • Tian Li,
  • Xin Wang

摘要

Introducing a synthetic H2/CO2 gas mixture into anaerobic systems is a promising strategy for C1 gas valorization, renewable energy storage, and sustainable chemical synthesis. However, systematic comparisons of inoculum sources under identical operational conditions remain limited. In this study, three inoculum sources, fermentation sludge (S1), lake sediment (S2), and brewery anaerobic sludge (S3), were compared for acetate production from CO2 and H2, with particular attention to microbial community succession and reactor stability. S3 showed the highest CO2 consumption rate (331 ± 4 mg CO2/(L·d)), cumulative CO2 fixation (7.8 ± 0.3 g/L), and acetate production efficiency (5.3% electron allocation to acetate), along with stable pH conditions (7.1 ± 0.3). These outcomes were associated with the rapid enrichment of genera that include known homoacetogenic species, mainly Clostridium and Acetobacterium, which together reached approximately 40% relative abundance in S3 after acclimation. The findings suggest that initial inoculum composition can influence the extent of homoacetogen enrichment and subsequent acetate production performance. In addition, the post-peak increase in the acetate-oxidizing genus Geobacter (an acetate consumer rather than an acetogen) in S3 points to a potential challenge for sustained product recovery in mixed-culture systems. Overall, these results provide insights for inoculum selection and process optimization in H2/CO2 fermentation systems for acetate production.