Kinetic Studies on Fermentative Production of Biofuel from Synthesis Gas Using<i>Clostridium ljungdahlii</i>

Mohammadi, Maedeh; Mohamed, Abdul Rahman; Najafpour, Ghasem; Younesi, Habibollah; Uzir, Mohamad Hekarl

doi:10.1155/2014/910590

Cited by 42 publications

(44 citation statements)

References 16 publications

(24 reference statements)

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“…E. limosum is capable of growing with CO as the sole energy source, with a doubling time of 7 h. However, with CO concentrations above 50% an inhibitory effect was observed, and the doubling time increased 2.6-fold and the final optical density decreased by 75% (26). When C. ljungdahlii was cultivated with CO, CO 2 , H 2 , and Ar (30%, 30%, 30, and 10%, respectively) in batch experiments, pressures above 1.0 atm led to inhibitory effects, which are most likely to be caused by CO (67).…”

Section: Discussionmentioning

confidence: 99%

CO Metabolism in the Acetogen Acetobacterium woodii

Bertsch

Müller

2015

Appl Environ Microbiol

104

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The Wood-Ljungdahl pathway allows acetogenic bacteria to grow on a number of one-carbon substrates, such as carbon dioxide, formate, methyl groups, or even carbon monoxide. Since carbon monoxide alone or in combination with hydrogen and carbon dioxide (synthesis gas) is an increasingly important feedstock for third-generation biotechnology, we studied CO metabolism in the model acetogen Acetobacterium woodii. When cells grew on H 2 -CO 2 , addition of 5 to 15% CO led to higher final optical densities, indicating the utilization of CO as a cosubstrate. However, the growth rate was decreased by the presence of small amounts of CO, which correlated with an inhibition of H 2 consumption. Experiments with resting cells revealed that the degree of inhibition of H 2 consumption was a function of the CO concentration. Since the hydrogen-dependent CO 2 reductase (HDCR) of A. woodii is known to be very sensitive to CO, we speculated that cells may be more tolerant toward CO when growing on formate, the product of the HDCR reaction. Indeed, addition of up to 25% CO did not influence growth rates on formate, while the final optical densities and the production of acetate increased. Higher concentrations (75 and 100%) led to a slight inhibition of growth and to decreasing rates of formate and CO consumption. Experiments with resting cells revealed that the HDCR is a site of CO inhibition. In contrast, A. woodii was not able to grow on CO as a sole carbon and energy source, and growth on fructose-CO or methanol-CO was not observed. There is a still-growing demand for sustainable biotechnological processes to cope with increasing needs for food, water, and energy for humankind. First-generation biotechnological processes all use food-based crops that compete for scarce cropland, fresh water, and fertilizers (1). Second-generation processes rely on biomass residues from forestry and agriculture that are used through lignocellulose fermentation. This is considered to play a major role in meeting the increasing demand, but it is still in its infancy (2). However, the process does produce the greenhouse gas CO 2 along with nonfermentable waste products. In an effort to combine reduction of greenhouse gases and global warming with the production of biocommodities, acetogenic bacteria have come into focus. They can convert CO 2 , H 2 , and CO to acetyl coenzyme A (acetyl-CoA), which is a starter molecule for various chemicals such as ethanol, acetate, 2,3 butanediol, and butanol (3-6). CO 2 , H 2 , and CO are the main components of synthesis gas (syngas), but the amounts of CO 2 , H 2 , and CO differ considerably, depending on the source. By gasification, virtually any organic matter can be converted to syngas. In addition, industrial waste gases contain syngas. Fermentation of syngas to ethanol is already used on a precommercial scale (7).Acetogenic bacteria have in common that they reduce CO 2 to acetic acid via the Wood-Ljungdahl pathway (WLP) (8). CO 2 reduction to acetyl-CoA proceeds via formate, formyl-tetrahydrofolic acid (TH...

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Section: Discussionmentioning

confidence: 99%

CO Metabolism in the Acetogen Acetobacterium woodii

Bertsch

Müller

2015

Appl Environ Microbiol

104

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“…This model was then used for studying the conversion rate of CO as a function of the gas loading rate and the volumetric mass transfer coefficient in a stirred tank reactor and a bubble column. The growth kinetics of the acetogen C. ljungdahlii were determined using several dual‐substrate kinetic models in order to study the effects of the initial pressure of syngas on the simultaneous consumption of H 2 and CO . Among all kinetic models tested in this study, the combination of Luong and Monod kinetics was found to give the best fitting for simulating growth on mixed substrates.…”

Section: Progress In Syngas Biomethanation and Ongoing Researchmentioning

confidence: 99%

Syngas biomethanation: state‐of‐the‐art review and perspectives

Grimalt‐Alemany

Skiadas

Gavala

2017

Biofuels Bioprod Bioref

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Signifi cant research efforts are currently being made worldwide to develop more effi cient biomethane production processes from a variety of waste streams. The biomethanation of biomassderived syngas can contribute to increasing the potential of methane production as it opens the way for the conversion of recalcitrant biomasses, generally not fully exploitable by anaerobic digestion systems. Additionally, this biological process presents several advantages over its analogous process of catalytic methanation such as the use of inexpensive biocatalysts, milder operational conditions, higher tolerance to the impurities of syngas, and higher product selectivity. However, there are still several challenges to be addressed for this technology to reach commercial stage. This work reviews the progress made over the last few years in syngas biomethanation processes in order to provide an overview of the current state of the art of this technology. The most relevant aspects determining the performance of syngas biomethanation processes are extensively discussed here, including microbial diversity and metabolic interactions in mixed microbial consortia, the infl uence of operating parameters and bioreactor designs, and the potential of modelling as a tool for the design and control of this bioprocess.

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“…The low K I of C. aceticum indicates a strong inhibition by CO whereas small K S indicates a high affinity to the substrate. Substrate inhibition kinetic studies with C. ljungdahlii revealed a K I of 494 mbar with the substrate inhibition model of Andrews (Mohammadi et al, ). Comparing C. aceticum with C. ljungdahlii shows the high sensitivity of C. aceticum toward CO inhibition (Najafpour & Younesi, ).…”

Section: Resultsmentioning

confidence: 94%

“…So far, only a very few number of studies investigated CO inhibition kinetics of acetogenic microorganisms like Blautia producta, Eubacterium limosum, and Clostridium ljungdahlii. As an example, C. ljungdahlii showed the highest CO conversion efficiency and highest growth rate at an initial CO partial pressure of 300 mbar (Chang, Kim, Lovitt, & Bang, 2001;Mohammadi, Mohamed, Najafpour, Younesi, & Uzir, 2014;Vega, Holmberg, Clausen, & Gaddy, 1988). On the other hand, there are also acetogens showing less or no substrate inhibition by CO, like C. carboxidivorans, which showed increased cell densities and ethanol productivities at increased CO partial pressure (Hurst & Lewis, 2010).…”

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confidence: 99%

Carbon monoxide conversion with Clostridium aceticum

Mayer

Schädler

Trunz

et al. 2018

Biotech & Bioengineering

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Carbon monoxide concentrations in syngas are often high, but tolerance toward CO varies a lot between homoacetogenic bacteria. Analysis of the autotrophic potential revealed that the first isolated acetogenic bacterium Clostridium aceticum was able to use CO as sole carbon and energy source for chemolithoautotrophic carbon fixation but simultaneously showed little tolerance to high CO concentrations. Not yet reported, autotrophic ethanol production by C. aceticum was discovered with CO as a substrate in batch processes. Growth rates estimated in batch processes at varying CO partial pressures were used to identify the CO inhibition kinetics of C. aceticum, using a substrate inhibition model. C. aceticum shows a strong CO inhibition with an optimum CO partial pressure of only 5.4 mbar in the gas phase at cell dry weight concentrations of up to 0.5 g·L . At optimum conditions, growth and acetate formation rates were estimated to be 0.24 hr and 0.52 g·g ·hr , respectively. Syngas fermentation at high partial pressures of up to 280 mbar CO in the inlet gas phase was enabled by applying a continuously operated stirred-tank bioreactor with submerged membranes with total cell retention. Around 70% CO conversion was achieved continuously in the membrane bioreactor with strongly CO inhibited C. aceticum resulting in space-time yields of up to 0.85 g·L ·hr acetate.

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Kinetic Studies on Fermentative Production of Biofuel from Synthesis Gas UsingClostridium ljungdahlii

Cited by 42 publications

References 16 publications

CO Metabolism in the Acetogen Acetobacterium woodii

CO Metabolism in the Acetogen Acetobacterium woodii

Syngas biomethanation: state‐of‐the‐art review and perspectives

Carbon monoxide conversion with Clostridium aceticum

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