Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation
Chain elongation reactor microbiomes produce valuable medium-chain carboxylates (MCC) from non-sterile residual substrates where lactate is a relevant intermediate. Gas supply has been shown to impact chain elongation performance. In the present study, the effect of nitrogen gas (N<sub>2</s...
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| Format: | Article |
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MDPI AG
2021-03-01
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| Series: | Fermentation |
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| Online Access: | https://www.mdpi.com/2311-5637/7/1/41 |
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| author | Carlos A. Contreras-Dávila Arielle Ali Cees J. N. Buisman David P. B. T. B. Strik |
| author_facet | Carlos A. Contreras-Dávila Arielle Ali Cees J. N. Buisman David P. B. T. B. Strik |
| author_sort | Carlos A. Contreras-Dávila |
| collection | DOAJ |
| description | Chain elongation reactor microbiomes produce valuable medium-chain carboxylates (MCC) from non-sterile residual substrates where lactate is a relevant intermediate. Gas supply has been shown to impact chain elongation performance. In the present study, the effect of nitrogen gas (N<sub>2</sub>) supply on lactate metabolism, conversion rates, biomass growth, and microbiome composition was evaluated in a lactate-fed upflow anaerobic reactor with continuous or intermittent N<sub>2</sub> gas supply. Successful MCC production was achieved with continuous N<sub>2</sub> gas supply at low superficial gas velocities (SGV) of 0.22 m∙h<sup>−1</sup>. Supplying N<sub>2</sub> at high SGV (>2 m∙h<sup>−1</sup>) either continuously (2.2 m∙h<sup>−1</sup>) or intermittently (3.6 m∙h<sup>−1</sup>) disrupted chain elongation, resulting in production of short-chain carboxylates (SCC), i.e., acetate, propionate, and n-butyrate. <i>Caproiciproducens</i>-dominated chain-elongating microbiomes enriched at low SGV were washed out at high SGV where <i>Clostridium tyrobutyricum</i>-dominated microbiomes thrived, by displaying higher lactate consumption rates. Suspended growth seemed to be dominant regardless of SGV and gas supply regime applied with no measurable sludge bed formed. The highest MCC production from lactate of 10 g COD∙L<sup>−1</sup>∙d<sup>−1</sup> with electron selectivities of 72 ± 5%was obtained without N<sub>2</sub> gas supply at a hydraulic retention time (HRT) of 1 day. The addition of 5 g∙L<sup>−1</sup> of propionate did not inhibit chain elongation, but rather boosted lactate conversion rates towards MCC with n-heptylate reaching 1.8 g COD∙L<sup>−1</sup>∙d<sup>−1</sup>. N<sub>2</sub> gas supply can be used for mixing purposes and to steer lactate metabolism to MCC or SCC production. |
| first_indexed | 2024-03-10T13:04:17Z |
| format | Article |
| id | doaj.art-d76daf19b4234f14b27ee2646a5ce075 |
| institution | Directory Open Access Journal |
| issn | 2311-5637 |
| language | English |
| last_indexed | 2024-03-10T13:04:17Z |
| publishDate | 2021-03-01 |
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| series | Fermentation |
| spelling | doaj.art-d76daf19b4234f14b27ee2646a5ce0752023-11-21T11:18:19ZengMDPI AGFermentation2311-56372021-03-01714110.3390/fermentation7010041Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain ElongationCarlos A. Contreras-Dávila0Arielle Ali1Cees J. N. Buisman2David P. B. T. B. Strik3Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The NetherlandsEnvironmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The NetherlandsEnvironmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The NetherlandsEnvironmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, The NetherlandsChain elongation reactor microbiomes produce valuable medium-chain carboxylates (MCC) from non-sterile residual substrates where lactate is a relevant intermediate. Gas supply has been shown to impact chain elongation performance. In the present study, the effect of nitrogen gas (N<sub>2</sub>) supply on lactate metabolism, conversion rates, biomass growth, and microbiome composition was evaluated in a lactate-fed upflow anaerobic reactor with continuous or intermittent N<sub>2</sub> gas supply. Successful MCC production was achieved with continuous N<sub>2</sub> gas supply at low superficial gas velocities (SGV) of 0.22 m∙h<sup>−1</sup>. Supplying N<sub>2</sub> at high SGV (>2 m∙h<sup>−1</sup>) either continuously (2.2 m∙h<sup>−1</sup>) or intermittently (3.6 m∙h<sup>−1</sup>) disrupted chain elongation, resulting in production of short-chain carboxylates (SCC), i.e., acetate, propionate, and n-butyrate. <i>Caproiciproducens</i>-dominated chain-elongating microbiomes enriched at low SGV were washed out at high SGV where <i>Clostridium tyrobutyricum</i>-dominated microbiomes thrived, by displaying higher lactate consumption rates. Suspended growth seemed to be dominant regardless of SGV and gas supply regime applied with no measurable sludge bed formed. The highest MCC production from lactate of 10 g COD∙L<sup>−1</sup>∙d<sup>−1</sup> with electron selectivities of 72 ± 5%was obtained without N<sub>2</sub> gas supply at a hydraulic retention time (HRT) of 1 day. The addition of 5 g∙L<sup>−1</sup> of propionate did not inhibit chain elongation, but rather boosted lactate conversion rates towards MCC with n-heptylate reaching 1.8 g COD∙L<sup>−1</sup>∙d<sup>−1</sup>. N<sub>2</sub> gas supply can be used for mixing purposes and to steer lactate metabolism to MCC or SCC production.https://www.mdpi.com/2311-5637/7/1/41microbial chain elongationmedium-chain carboxylateslactaten-caproaten-heptylaten-caprylate |
| spellingShingle | Carlos A. Contreras-Dávila Arielle Ali Cees J. N. Buisman David P. B. T. B. Strik Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation Fermentation microbial chain elongation medium-chain carboxylates lactate n-caproate n-heptylate n-caprylate |
| title | Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation |
| title_full | Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation |
| title_fullStr | Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation |
| title_full_unstemmed | Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation |
| title_short | Lactate Metabolism and Microbiome Composition Are Affected by Nitrogen Gas Supply in Continuous Lactate-Based Chain Elongation |
| title_sort | lactate metabolism and microbiome composition are affected by nitrogen gas supply in continuous lactate based chain elongation |
| topic | microbial chain elongation medium-chain carboxylates lactate n-caproate n-heptylate n-caprylate |
| url | https://www.mdpi.com/2311-5637/7/1/41 |
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