Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed
Abstract Background Duckweeds (Lemnaceae) are efficient aquatic plants for wastewater treatment due to their high nutrient-uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweeds have also gained p...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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BMC
2018-10-01
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| Series: | Biotechnology for Biofuels |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s13068-018-1278-6 |
| _version_ | 1811243768492326912 |
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| author | Ozgul Calicioglu Michael J. Shreve Tom L. Richard Rachel A. Brennan |
| author_facet | Ozgul Calicioglu Michael J. Shreve Tom L. Richard Rachel A. Brennan |
| author_sort | Ozgul Calicioglu |
| collection | DOAJ |
| description | Abstract Background Duckweeds (Lemnaceae) are efficient aquatic plants for wastewater treatment due to their high nutrient-uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweeds have also gained popularity as a biofuel feedstock for thermochemical conversion and alcohol fermentation. However, studies on the acidogenic anaerobic digestion of duckweed into carboxylic acids, another group of chemicals which are precursors of higher-value chemicals and biofuels, are lacking. In this study, a series of laboratory batch experiments were performed to determine the favorable operating conditions (i.e., temperature and pH) to maximize carboxylic acid production from wastewater-derived duckweed during acidogenic digestion. Batch reactors with 25 g/l solid loading were operated anaerobically for 21 days under mesophilic (35 °C) or thermophilic (55 °C) conditions at an acidic (5.3) or basic (9.2) pH. At the conclusion of the experiment, the dominant microbial communities under various operating conditions were assessed using high-throughput sequencing. Results The highest duckweed–carboxylic acid conversion of 388 ± 28 mg acetic acid equivalent per gram volatile solids was observed under mesophilic and basic conditions, with an average production rate of 0.59 g/l/day. This result is comparable to those reported for acidogenic digestion of other organics such as food waste. The superior performance observed under these conditions was attributed to both chemical treatment and microbial bioconversion. Hydrogen recovery was only observed under acidic thermophilic conditions, as 23.5 ± 0.5 ml/g of duckweed volatile solids added. More than temperature, pH controlled the overall structure of the microbial communities. For instance, differentially abundant enrichments of Veillonellaceae acidaminococcus were observed in acidic samples, whereas enrichments of Clostridiaceae alkaliphilus were found in the basic samples. Acidic mesophilic conditions were found to enrich acetoclastic methanogenic populations over processing times longer than 10 days. Conclusions Operating conditions have a significant effect on the yield and composition of the end products resulting from acidogenic digestion of duckweed. Wastewater-derived duckweed is a technically feasible alternative feedstock for the production of advanced biofuel precursors; however, techno-economic analysis is needed to determine integrated full-scale system feasibility and economic viability. |
| first_indexed | 2024-04-12T14:14:18Z |
| format | Article |
| id | doaj.art-77fcd1711e904942a4cb091f1fd4b3d2 |
| institution | Directory Open Access Journal |
| issn | 1754-6834 |
| language | English |
| last_indexed | 2024-04-12T14:14:18Z |
| publishDate | 2018-10-01 |
| publisher | BMC |
| record_format | Article |
| series | Biotechnology for Biofuels |
| spelling | doaj.art-77fcd1711e904942a4cb091f1fd4b3d22022-12-22T03:29:47ZengBMCBiotechnology for Biofuels1754-68342018-10-0111111910.1186/s13068-018-1278-6Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweedOzgul Calicioglu0Michael J. Shreve1Tom L. Richard2Rachel A. Brennan3Department of Civil and Environmental Engineering, The Pennsylvania State UniversityDepartment of Civil and Environmental Engineering, The Pennsylvania State UniversityDepartment of Agricultural and Biological Engineering, The Pennsylvania State UniversityDepartment of Civil and Environmental Engineering, The Pennsylvania State UniversityAbstract Background Duckweeds (Lemnaceae) are efficient aquatic plants for wastewater treatment due to their high nutrient-uptake capabilities and resilience to severe environmental conditions. Combined with their rapid growth rates, high starch, and low lignin contents, duckweeds have also gained popularity as a biofuel feedstock for thermochemical conversion and alcohol fermentation. However, studies on the acidogenic anaerobic digestion of duckweed into carboxylic acids, another group of chemicals which are precursors of higher-value chemicals and biofuels, are lacking. In this study, a series of laboratory batch experiments were performed to determine the favorable operating conditions (i.e., temperature and pH) to maximize carboxylic acid production from wastewater-derived duckweed during acidogenic digestion. Batch reactors with 25 g/l solid loading were operated anaerobically for 21 days under mesophilic (35 °C) or thermophilic (55 °C) conditions at an acidic (5.3) or basic (9.2) pH. At the conclusion of the experiment, the dominant microbial communities under various operating conditions were assessed using high-throughput sequencing. Results The highest duckweed–carboxylic acid conversion of 388 ± 28 mg acetic acid equivalent per gram volatile solids was observed under mesophilic and basic conditions, with an average production rate of 0.59 g/l/day. This result is comparable to those reported for acidogenic digestion of other organics such as food waste. The superior performance observed under these conditions was attributed to both chemical treatment and microbial bioconversion. Hydrogen recovery was only observed under acidic thermophilic conditions, as 23.5 ± 0.5 ml/g of duckweed volatile solids added. More than temperature, pH controlled the overall structure of the microbial communities. For instance, differentially abundant enrichments of Veillonellaceae acidaminococcus were observed in acidic samples, whereas enrichments of Clostridiaceae alkaliphilus were found in the basic samples. Acidic mesophilic conditions were found to enrich acetoclastic methanogenic populations over processing times longer than 10 days. Conclusions Operating conditions have a significant effect on the yield and composition of the end products resulting from acidogenic digestion of duckweed. Wastewater-derived duckweed is a technically feasible alternative feedstock for the production of advanced biofuel precursors; however, techno-economic analysis is needed to determine integrated full-scale system feasibility and economic viability.http://link.springer.com/article/10.1186/s13068-018-1278-6Volatile fatty acidsAcidogenic digestionCarboxylate platformBiohydrogenDuckweedLemna obscura |
| spellingShingle | Ozgul Calicioglu Michael J. Shreve Tom L. Richard Rachel A. Brennan Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed Biotechnology for Biofuels Volatile fatty acids Acidogenic digestion Carboxylate platform Biohydrogen Duckweed Lemna obscura |
| title | Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| title_full | Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| title_fullStr | Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| title_full_unstemmed | Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| title_short | Effect of pH and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| title_sort | effect of ph and temperature on microbial community structure and carboxylic acid yield during the acidogenic digestion of duckweed |
| topic | Volatile fatty acids Acidogenic digestion Carboxylate platform Biohydrogen Duckweed Lemna obscura |
| url | http://link.springer.com/article/10.1186/s13068-018-1278-6 |
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