| NSF Org: |
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems |
| Recipient: |
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| Initial Amendment Date: | June 15, 2014 |
| Latest Amendment Date: | June 15, 2014 |
| Award Number: | 1438042 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Raymond Adomaitis
CBET Division of Chemical, Bioengineering, Environmental, and Transport Systems ENG Directorate for Engineering |
| Start Date: | October 1, 2014 |
| End Date: | September 30, 2019 (Estimated) |
| Total Intended Award Amount: | $150,000.00 |
| Total Awarded Amount to Date: | $150,000.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
1350 BEARDSHEAR HALL AMES IA US 50011-2103 (515)294-5225 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
IA US 50011-2207 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Proc Sys, Reac Eng & Mol Therm |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.041 |
ABSTRACT
Collaborative Research: Use of 13C-labeling and flux modeling to analyze metabolic reactions and gas-liquid mass transfer during syngas fermentations
PI: Ziyou Wen (Iowa State University)
Yinjie Tang (Washington University at St. Louis)
Proposal IDs: 1438042 (Wen), 1438125 (Tang)
Abstract
Sugar-based feedstocks or oil-rich crops are primarily used in today?s biofuel industry. These biofuel production approaches pose a threat to the global food supply. As an alternative, this research will use inexpensive lignocellulosic biomass (e.g., corn stover or switchgrass) as a feedstock for producing biofuel. The conversion process proposed is based on the gasification of the biomass into syngas (mainly CO, CO2 and H2), and the subsequent fermentation of those gaseous molecules into fuels (such as ethanol). The objectives of this project aim to address two important fundamental issues in syngas fermentations: 1. the mass transfer limitations of transporting gaseous substrates (CO, CO2 and H2) into microbes; 2. the bottleneck enzymes in microbes to convert syngas into biofuels. This study will advance the current research on syngas fermentation using methods in systems biology. By linking macroscopic syngas mass transfer conditions to intracellular enzyme reaction rates in biofuel producing microbes, a holistic view of syngas fermentation will be provided. Ultimately, this project will also produce guidelines for developing other gas-to-liquid biorefineries.
Transient 13C techniques and metabolic models will be used to examine syngas mass transfer and biological utilization by Clostridium carboxidivorans. The first task will incorporate 13C tracing to accurately determine gas-liquid mass transfer parameters and analyze their influence on cellular carbon assimilation. The second task will be to develop a flux balance model to predict microbial growth and ethanol production in response to bioreactor control parameters, such as gas flow rate and mixing. The third task will include pilot scale syngas fermentation at the flux-model-predicted conditions. This project will determine the mass transfer coefficient (KLa) of different syngas composition under complex fermentation conditions, and improve the understandings of the bioavailability of gaseous substrates under various bioreactor operations. Meanwhile, 13C-assisted flux balance analysis will also reveal key enzymatic reactions, which control syngas bioconversion into ethanol. The combination of a metabolic flux model with gas-liquid mass transfer dynamics will offer rational approaches for further work in syngas fermentation development. This research is a partnership between Iowa State University and Washington University in St. Louis. The PIs, with their complementary skills, will provide excellent training and interdisciplinary educational opportunities (including summer research, workshop, international studies, etc.) for students to study reaction engineering, bioprocessing, analytical chemistry, and metabolic modeling.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Intellectual merit: Syngas fermentation can produce fuels and chemicals. Developing a successful syngas fermentation process still faces challenges in both engineering problems (i.e., gas-liquid mass transfer limitations) and biological bottlenecks (i.e., intrinsic cellular metabolism). This study investigated these two factors in syngas fermentations of Clostridium carboxidivorans P7 using a 13C-based techniques. The aim is to maximize ethanol production through optimizing and balancing gas-liquid mass transfer in the bioreactor and metabolic flux in the cells. It was found that whether the fermentation performance is limited by mass transfer at bioreactor level or by metabolism of substrates at cellular level depends on the flow rate of syngas. Under a working volume of 250 mL fermentation scale, flow rate of 1-10 mL/min resulted in mass transfer limitation, while 10-20 mL/min led to a cell metabolism flux limitation. The fermentation of P7 cells under different gas compositions was also studied. It was found the lack of either CO or CO2 in syngas impaired fermentation performance; while high H2 content could improve alcohol productions and carbon assimilation. At later stage of fermentation, acetate was consumed for synthesis of C4 compounds (butyrate and butanol). This study demonstrates that the integration of fermentation operations to isotopic tracing can help engineers understand and design effective bioprocesses under complex influential factors.
Broader impacts: This research is a partnership between Iowa State University and Washington University in St. Louis. The project has expanded the scope of systems biology applications to industrial fermentations, and it may provide new guidelines for other biorefineries. Meanwhile, the PIs have provided excellent training and interdisciplinary educational opportunities for graduate students and undergraduates to study molecular engineering, bioenergy, bioprocessing, analytical chemistry, and metabolic modeling. The project has supported to multiple graduate students with several significant publications.
Last Modified: 12/28/2019
Modified by: Zhiyou Wen
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