Effect of Cysteine, Yeast Extract, pH Regulation and Gas Flow on Acetate and Ethanol Formation and Growth Profiles of Clostridium ljungdahlii Syngas Fermentation

ABSTRACTThe fermentation of synthesis gas, or syngas, which consists mainly of CO, CO2 and H2 by acetogenic bacteria has the potential to help in transitioning from a fossil-fuel-based to a renewable bio-economy. Clostridium ljungdahlii, one of such microorganisms, has as main fermentation products acetate and ethanol. Multiple research efforts have been directed towards understanding how the metabolism and the product formation of this, and other acetogenic bacteria, can be directed towards increasing productivities and yields; nonetheless, transferring those findings to a particular set-up can prove challenging. This study used a well-established and robust fed-batch fermentation system with C. ljungdahlii to look into the effects of different fermentation pH profiles, gas flow, and the supplementation with additional yeast extract or cysteine on growth, product formation ratios, yields, and productivities, as well as gas consumption. Neither yeast extract nor cysteine supplementation had a noticeable impact on cell growth, product formation or overall gas consumption. The lowering of the pH proved mainly detrimental, with decreased productivities and no improvement in ethanol ratios. The most notable shift towards ethanol was achieved by the combination of lowering both the pH and the gas flow after 24 h, but with the caveat of lower productivity. The obtained results, unexpected to some extent, highlight the necessity for a better understanding of the physiology and the metabolic regulation of acetogenic bacteria in order for this process to become more industrially relevant.

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Evaluation of Media Components and Process Parameters in a Sensitive and Robust Fed-Batch Syngas Fermentation System with Clostridium ljungdahlii

Fermentation ◽

10.3390/fermentation6020061 ◽

2020 ◽

Vol 6 (2) ◽

pp. 61 ◽

Cited By ~ 1

Author(s):

Alba Infantes ◽

Michaela Kugel ◽

Anke Neumann

Keyword(s):

Yeast Extract ◽

Process Parameters ◽

Gas Flow ◽

Limiting Factor ◽

Syngas Fermentation ◽

Fermentation Products ◽

Clostridium Ljungdahlii ◽

Lower Productivity ◽

Acetogenic Bacteria ◽

Gas Consumption

The fermentation of synthesis gas, or syngas, by acetogenic bacteria can help in transitioning from a fossil-fuel-based to a renewable bioeconomy. The main fermentation products of Clostridium ljungdahlii, one of such microorganisms, are acetate and ethanol. A sensitive, robust and reproducible system was established for C. ljungdahlii syngas fermentation, and several process parameters and medium components (pH, gas flow, cysteine and yeast extract) were investigated to assess its impact on the fermentation outcomes, as well as real time gas consumption. Moreover, a closed carbon balance could be achieved with the data obtained. This system is a valuable tool to detect changes in the behavior of the culture. It can be applied for the screening of strains, gas compositions or media components, for a better understanding of the physiology and metabolic regulation of acetogenic bacteria. Here, it was shown that neither yeast extract nor cysteine was a limiting factor for cell growth since their supplementation did not have a noticeable impact on product formation or overall gas consumption. By combining the lowering of both the pH and the gas flow after 24 h, the highest ethanol to acetate ratio was achieved, but with the caveat of lower productivity.

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Side-by-Side Comparison of Clean and Biomass-Derived, Impurity-Containing Syngas as Substrate for Acetogenic Fermentation with Clostridium ljungdahlii

Fermentation ◽

10.3390/fermentation6030084 ◽

2020 ◽

Vol 6 (3) ◽

pp. 84

Author(s):

Alba Infantes ◽

Michaela Kugel ◽

Klaus Raffelt ◽

Anke Neumann

Keyword(s):

Biomass Gasification ◽

Product Formation ◽

Inhibitory Effects ◽

Fed Batch ◽

Gaseous Mixtures ◽

Clostridium Ljungdahlii ◽

Acetogenic Bacteria ◽

Fed Batch Fermentation ◽

Total Productivity ◽

The Impact

Syngas, the product of biomass gasification, can play an important role in moving towards the production of renewable chemical commodities, by using acetogenic bacteria to ferment those gaseous mixtures. Due to the complex and changing nature of biomass, the composition and the impurities present in the final biomass-derived syngas will vary. Because of this, it is important to assess the impact of these factors on the fermentation outcome, in terms of yields, productivity, and product formation and ratio. In this study, Clostridium ljungdahlii was used in a fed-batch fermentation system to analyze the effect of three different biomass-derived syngases, and to compare them to equivalent, clean syngas mixtures. Additionally, four other clean syngas mixtures were used, and the effects on product ratio, productivity, yield, and growth were documented. All biomass-derived syngases were suitable to be used as substrates, without experiencing any complete inhibitory effects. From the obtained results, it is clear that the type of syngas, biomass-derived or clean, had the greatest impact on product formation ratios, with all biomass-derived syngases producing more ethanol, albeit with lesser total productivity.

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Directing Clostridium ljungdahlii fermentation products via hydrogen to carbon monoxide ratio in syngas

Biomass and Bioenergy ◽

10.1016/j.biombioe.2019.03.011 ◽

2019 ◽

Vol 124 ◽

pp. 95-101 ◽

Cited By ~ 13

Author(s):

Joshua Jack ◽

Jonathan Lo ◽

Pin-Ching Maness ◽

Zhiyong Jason Ren

Keyword(s):

Carbon Monoxide ◽

Fermentation Products ◽

Clostridium Ljungdahlii

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Electron availability in CO 2 , CO and H 2 mixtures constrains flux distribution, energy management and product formation in Clostridium ljungdahlii

Microbial Biotechnology ◽

10.1111/1751-7915.13625 ◽

2020 ◽

Vol 13 (6) ◽

pp. 1831-1846

Author(s):

Maria Hermann ◽

Attila Teleki ◽

Sandra Weitz ◽

Alexander Niess ◽

Andreas Freund ◽

...

Keyword(s):

Energy Management ◽

Flux Distribution ◽

Product Formation ◽

Clostridium Ljungdahlii ◽

Distribution Energy

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The Design and Some Emission Characteristics of an Economical dc Arc Plasmajet Excitation Source for Solution Analysis

Applied Spectroscopy ◽

10.1366/000370270774371769 ◽

1970 ◽

Vol 24 (2) ◽

pp. 197-205 ◽

Cited By ~ 63

Author(s):

S. E. Valente ◽

W. G. Schrenk

Keyword(s):

Gas Flow ◽

Matrix Effects ◽

Detection Limits ◽

Inert Gas ◽

Excitation Source ◽

Analytical Response ◽

Gas Consumption ◽

Moderate Sensitivity ◽

Dc Arc ◽

Better Than

The de-arc plasmajet has been applied to a large number of emission problems since its introduction in 1959 because it offers reduced matrix effects, stability, and moderate sensitivity. However, its use has been significantly limited due to operating costs associated with its high inert gas flow rates. A new excitation source, based on the principle of the plasma jet, has been developed that can operate at a much lower cost. The source operates from a conventional dc-arc power supply and uses commercially available electrodes. Total inert gas consumption is less than 2.5 liters/min. Stability of the source is better than 1% and reproducibility is approximately 4%. An excitation temperature of 5800 K was calculated from the relative intensities of several vanadium lines. The source can be operated continuously for several hours at a time. Design and some characteristics of the arc are presented. Detection limits are given for 12 elements. Six of the elements (Ca, Cr, Fe, Li, Ni, and Y) have detection limits below 10 ng/ml. Analytical response for the elements studied is linear over a wide concentration range. A calibration curve for Ca is presented which is linear over more than four orders of magnitude.

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

The Scientific World JOURNAL ◽

10.1155/2014/910590 ◽

2014 ◽

Vol 2014 ◽

pp. 1-8 ◽

Cited By ~ 21

Author(s):

Maedeh Mohammadi ◽

Abdul Rahman Mohamed ◽

Ghasem D. Najafpour ◽

Habibollah Younesi ◽

Mohamad Hekarl Uzir

Keyword(s):

Cell Growth ◽

Synthesis Gas ◽

Uptake Rate ◽

Kinetic Studies ◽

Product Formation ◽

Volterra Model ◽

Substrate Uptake ◽

Growth Substrate ◽

Clostridium Ljungdahlii ◽

Batch Bioreactors

The intrinsic growth, substrate uptake, and product formation biokinetic parameters were obtained for the anaerobic bacterium,Clostridium ljungdahlii, grown on synthesis gas in various pressurized batch bioreactors. A dual-substrate growth kinetic model using Luong for CO and Monod for H2was used to describe the growth kinetics of the bacterium on these substrates. The maximum specific growth rate (μmax= 0.195 h−1) and Monod constants for CO (Ks,CO= 0.855 atm) and H2(Ks,H2= 0.412 atm) were obtained. This model also accommodated the CO inhibitory effects on cell growth at high CO partial pressures, where no growth was apparent at high dissolved CO tensions (PCO∗>0.743 atm). The Volterra model, Andrews, and modified Gompertz were, respectively, adopted to describe the cell growth, substrate uptake rate, and product formation. The maximum specific CO uptake rate (qmax= 34.364 mmol/gcell/h), CO inhibition constant (KI= 0.601 atm), and maximum rate of ethanol (Rmax= 0.172 mmol/L/h atPCO= 0.598 atm) and acetate (Rmax= 0.096 mmol/L/h atPCO= 0.539 atm) production were determined from the applied models.

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Description and Characterization of a Linear-Flow Outer Gas Flow Torch for Inductively Coupled Plasma Emission Spectroscopy

Applied Spectroscopy ◽

10.1366/0003702924123999 ◽

1992 ◽

Vol 46 (8) ◽

pp. 1245-1250 ◽

Cited By ~ 5

Author(s):

Gary D. Rayson ◽

Daniel Yang Shen

Keyword(s):

Inductively Coupled Plasma ◽

Emission Spectroscopy ◽

Gas Flow ◽

Gas Flows ◽

Linear Flow ◽

Inductively Coupled ◽

Consumption Rates ◽

Gas Consumption ◽

Plasma Emission Spectroscopy

An inductively coupled plasma torch has been developed which utilizes linear coolant gas flows and is operated at reduced applied power levels and argon gas consumption rates. The linear flow torch (LiFT) is constructed by the addition of a machined insert between the outer and intermediate tubing of a conventional tangential flow torch (TaFT). This LiFT configuration has been demonstrated to be capable of providing improved detection limits, in comparison to a TaFT, at conditions of lower power and gas flow. Under those conditions the LiFT was also demonstrated to produce less severe interferences to analyte emission in the presence of an easily ionizable element.

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The impact of fresh gas flow on wash-in, wash-out time and gas consumption for sevoflurane and desflurane, comparing two anaesthesia machines, a test-lung study.

F1000Research ◽

10.12688/f1000research.13064.2 ◽

2017 ◽

Vol 6 ◽

pp. 1997 ◽

Cited By ~ 2

Author(s):

Fredrik Leijonhufvud ◽

Fredrik Jöneby ◽

Jan G. Jakobsson

Keyword(s):

Gas Flow ◽

Anaesthetic Agent ◽

Point Of View ◽

Low Flow ◽

Test Lung ◽

Minimal Alveolar Concentration ◽

Flow Rates ◽

Optimal Flow ◽

Gas Consumption ◽

The Impact

Low-flow anaesthesia is considered beneficial for the patient and the environment, and it is cost reducing due to reduced anaesthetic gas consumption. An initial high-flow to saturate the circle system ( wash-in) is desirable from a clinical point of view. We measured the wash-in and wash-out times (time to saturate and to eliminate the anaesthetic agent, AA), for sevoflurane and desflurane, in a test-lung with fixed 3 MAC vaporizer setting at different fresh gas flow (FGF) and calculated the consumption of AA. We tried to find an optimal flow rate for speed and gas consumption, comparing two anaesthesia machines (AMs): Aisys and Flow-i. Time to reach 1 minimal alveolar concentration (MAC) (wash-in) decreased (p<0.05) at higher flow rates (1 – 2 – 4) but plateaued at 4-4.8 l/min. The consumption of AA was at its lowest around 4-4.8 l/min (optimal flow) for all but the Aisys /desflurane group. Wash-out times decreased as FGF increased, until reaching plateau at FGF of 4-6 l/min. Aisys had generally shorter wash-in times at flow rates < 4 l/min as well as lower consumption of AA. At higher flow rates there were little difference between the AMs. The “optimal FGF” for wash-out, elimination of gas from the test-lung and circle system, plateaued with no increase in speed beyond 6 l/min. A fresh gas flow of 4 l/min. seems “optimal” taking speed to reach a 1 MAC ET and gas consumption into account during wash-in with a fixed 3 MAC vaporizer setting, and increasing fresh gas flow beyond 6 l/min does not seem to confirm major benefit during wash-out.

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