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. 2025 Apr 29;12(5):470.
doi: 10.3390/bioengineering12050470.

Enhancing Gas Fermentation Efficiency via Bioaugmentation with Megasphaera sueciensis and Clostridium carboxidivorans

Clemens Hiebl  1 , Dominik Pinner  1 , Hannes Konegger  1 , Franziska Steger  1 , Dina Mohamed  2 , Werner Fuchs  1
Affiliations

Enhancing Gas Fermentation Efficiency via Bioaugmentation with Megasphaera sueciensis and Clostridium carboxidivorans

Clemens Hiebl et al. Bioengineering (Basel). .

Abstract

Gas fermentation aims to fix CO2 into higher-value compounds, such as short or medium-chain fatty acids or alcohols. In this context, the use of mixed microbial consortia presents numerous advantages, including increased resilience and adaptability. The current study aimed to improve the performance of an enriched mixed microbial population via bioaugmentation with Megasphaera sueciensis and Clostridium carboxidivorans to improve the metabolite spectrum. The initial fermentation in trickle-bed reactors mainly yielded acetate, a low-value compound. Introducing M. sueciensis, which converts acetate into higher-chain fatty acids, shifted production toward butyrate (up to 3.2 g/L) and caproate (1.1 g/L). The presence of M. sueciensis was maintained even after several media swaps, showing its ability to establish itself as a permanent part of the microbial community. Metataxonomic analysis confirmed the successful integration of M. sueciensis into the mixed culture, with it becoming a dominant member of the Veillonellaceae family. In contrast, bioaugmentation with C. carboxidivorans was unsuccessful. Although this strain is known for producing alcohols, such as butanol and hexanol, it did not significantly enhance alcohol production, as attempts to establish it within the microbial consortium were unsuccessful. Despite these mixed results, bioaugmentation with complementary microbial capabilities remains a promising strategy to improve gas fermentation efficiency. This approach may enhance the economic feasibility of industrial-scale renewable chemical production.

Keywords: Clostridium carboxidivorans; Megasphaera sueciensis; bioaugmentation; gas fermentation; medium-chain volatile fatty acids; mixed microbial culture.

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Conflict of interest statement

The authors declare no conflicts of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the results.

Figures

Figure 1
Figure 1
Scheme of the trickle-bed reactor setup employed in the experiments.
Figure 2
Figure 2
Course of metabolite concentration in CHER I; Indigo circles: acetate, orange squares: butyrate, green diamonds: caproate, blue triangles: ethanol; Key events: day 7—inoculation with M. sueciensis, day 49—media swap, day 119—media swap after fixing leakage; day 265—media swap. Sample for Metataxonomic analysis taken at day 315.
Figure 3
Figure 3
Course of metabolite concentration in CHER II; Indigo circles: acetate, orange squares: butyrate, green diamonds: caproate, blue triangles: ethanol; Key events: day 0—inoculation with mixed culture (CHER I), day 150—media swap. Sample for metataxonomic analysis taken on day 205.
Figure 4
Figure 4
Course of metabolite concentration in CHER III; Indigo circles: acetate, orange squares: butyrate, green diamonds: caproate, blue triangles: ethanol; Key events: day 0—inoculation with mixed culture (CHER I), day 150—media swap.
Figure 5
Figure 5
Course of metabolite concentration in CHER IV; Indigo circles: acetate, orange squares: butyrate, green diamonds: caproate, blue triangles: ethanol; Key events: day 0—inoculation with mixed culture (CHER I) + pure culture of C. carboxidivorans, day 150—media swap.
Figure 6
Figure 6
Metataxonomic analysis of the culture used as inoculum; Data from Steger et al., 2022 [20].
Figure 7
Figure 7
Metataxonomic analysis of CHER I at the family tree level (sample collected at day 315).
Figure 8
Figure 8
Metataxonomic analysis of CHER II at the family tree level (sample collected at day 204 of fermentation).
Figure 9
Figure 9
Metataxonomic analysis of CHER III at the family tree level (sample collected at day 204).
Figure 10
Figure 10
Metataxonomic analysis of CHER IV at the family tree level (sample collected at day 200).
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