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Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia.

ABSTRACT: Dark fermentative biohydrogen (H2) production could become a key technology for providing renewable energy. Until now, the H2 yield is restricted to 4 moles of H2 per mole of glucose, referred to as the "Thauer limit". Here we show, that precision design of artificial microbial consortia increased the H2 yield to 5.6?mol?mol-1 glucose, 40% higher than the Thauer limit. In addition, the volumetric H2 production rates of our defined artificial consortia are superior compared to any mono-, co- or multi-culture system reported to date. We hope this study to be a major leap forward in the engineering of artificial microbial consortia through precision design and provide a breakthrough in energy science, biotechnology and ecology. Constructing artificial consortia with this drawing-board approach could in future increase volumetric production rates and yields of other bioprocesses. Our artificial consortia engineering blueprint might pave the way for the development of a H2 production bioindustry.

SUBMITTER: Ergal I

PROVIDER: S-EPMC7429504 | biostudies-literature | 2020 Aug

REPOSITORIES: biostudies-literature

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Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia.

Ergal İpek İ Gräf Oliver O Hasibar Benedikt B Steiner Michael M Vukotić Sonja S Bochmann Günther G Fuchs Werner W Rittmann Simon K-M R SKR

Communications biology 20200814 1

Dark fermentative biohydrogen (H2) production could become a key technology for providing renewable energy. Until now, the H2 yield is restricted to 4 moles of H2 per mole of glucose, referred to as the "Thauer limit". Here we show, that precision design of artificial microbial consortia increased the H2 yield to 5.6 mol mol-1 glucose, 40% higher than the Thauer limit. In addition, the volumetric H2 production rates of our defined ...[more]

PMID: 32796915

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Project description:Background:The production of ethanol through the biochemical conversion of syngas, a mixture of H2, CO and CO2, has been typically studied using pure cultures. However, mixed microbial consortia may offer a series of benefits such as higher resilience and adaptive capacity, and non-sterile operation, all of which contribute to reducing the utility consumption when compared to pure culture-based processes. This work focuses on the study of strategies for the enrichment of mixed microbial consortia with high ethanologenic potential, investigating the effect of the operational conditions (pH and yeast extract addition) on both the ethanol yield and evolution of the microbial community along the enrichment process. The pH was selected as the main driver of the enrichment as it was expected to be a crucial parameter for the selection of carboxydotrophic bacteria with high ethanologenic potential. Additionally, a thermodynamic analysis of the network of biochemical reactions carried out by syngas-converting microbial consortia was performed and the potential of using thermodynamics as a basis for the selection of operational parameters favoring a specific microbial activity was evaluated. Results:All enriched consortia were dominated by the genus Clostridium with variable microbial diversity and species composition as a function of the enrichment conditions. The ethanologenic potential of the enriched consortia was observed to increase as the initial pH was lowered, achieving an ethanol yield of 59.2?±?0.2% of the theoretical maximum in the enrichment at pH 5. On the other hand, yeast extract addition did not affect the ethanol yield, but triggered the production of medium-chain fatty acids and alcohols. The thermodynamic analysis of the occurring biochemical reactions allowed a qualitative prediction of the activity of microbial consortia, thus enabling a more rational design of the enrichment strategies targeting specific activities. Using this approach, an improvement of 22.5% over the maximum ethanol yield previously obtained was achieved, reaching an ethanol yield of 72.4?±?2.1% of the theoretical maximum by increasing the initial acetate concentration in the fermentation broth. Conclusions:This study demonstrated high product selectivity towards ethanol using mixed microbial consortia. The thermodynamic analysis carried out proved to be a valuable tool for interpreting the metabolic network of microbial consortia-driven processes and designing microbial-enrichment strategies targeting specific biotransformations.

Project description:Abstract Capillary biofilm reactors (CBRs) are attractive for growing photoautotrophic bacteria as they allow high cell‐density cultivation. Here, we evaluated the CBR system's suitability to grow an artificial consortium composed of Synechocystis sp. PCC 6803 and Pseudomonas sp. VBL120. The impact of reactor material, flow rate, pH, O2, and medium composition on biomass development and long‐term biofilm stability at different reactor scales was studied. Silicone was superior over other materials like glass or PVC due to its excellent O2 permeability. High flow rates of 520 μL min−1 prevented biofilm sloughing in 1 m capillary reactors, leading to a 54% higher biomass dry weight combined with the lowest O2 concentration inside the reactor compared to standard operating conditions. Further increase in reactor length to 5 m revealed a limitation in trace elements. Increasing trace elements by a factor of five allowed for complete surface coverage with a biomass dry weight of 36.8 g m−2 and, thus, a successful CBR scale‐up by a factor of 25. Practical application: Cyanobacteria use light energy to upgrade CO2, thereby holding the potential for carbon‐neutral production processes. One of the persisting challenges is low cell density due to light limitations and O2 accumulation often occurring in established flat panel or tubular photobioreactors. Compared to planktonic cultures, much higher cell densities (factor 10 to 100) can be obtained in cyanobacterial biofilms. The capillary biofilm reactor (CBR) offers good growth conditions for cyanobacterial biofilms, but its applicability has been shown only on the laboratory scale. Here, a first scale‐up study based on sizing up was performed, testing the feasibility of this system for large‐scale applications. We demonstrate that by optimizing nutrient supply and flow conditions, the system could be enlarged by factor 25 by enhancing the length of the reactor. This reactor concept, combined with cyanobacterial biofilms and numbering up, holds the potential to be applied as a flexible, carbon‐neutral production platform for value‐added compounds.

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Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia.

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Biohydrogen production beyond the Thauer limit by precision design of artificial microbial consortia.

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