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Biofuel Production from Carbon monoxide

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Page 1: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

Biofuel Production from Carbon monoxide

Page 2: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

Homepage1.Background2.Executive Summary3.Introduction4.Summary

4.1 Article 1 4.2 Article 25. Comparative Analysis6. References

(Background picture obtained from http://projectbiofuel.blogspot.com.au/) Next Page

Page 3: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

1. Background

Hello everyone! My name is Geetika Kalleechurn and I am

currently doing a major in Biotechnology and Molecular

Biology.

My topic is biofuel production from acetogenic bacteria

that use carbon monoxide as a carbon source and

synthesise ethanol.

I chose this topic as I found the idea of carbon monoxide

utilization in biofuel production quite fascinating and I hope

you do too!

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Homepage

1.Background2.Executive Summary3.Introduction4.Summary

4.1 Article 4.2 Article 5. Comparative Analysis6. References

Page 4: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

2. Executive Summary

This work involves a comparative analysis of two experiments

based on the parameters affecting the growth of acetogenic

Clostridium species that synthesise ethanol via syngas

fermentation. The aim is to understand the effects of variation

in parameters on the growth of the Clostridium species in order

to optimise ethanol production from syngas fermentation.

(Image obtained from blogs.cleanfuelsdc.org) Previous Next

Homepage

1.Background2.Executive Summary3.Introduction4.Summary

4.1 Article 4.2 Article 5. Comparative Analysis6. References

Page 5: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

3. Introduction

With a worldwide increase in the consumption and gradual diminishing of fossil fuels, the need for renewable energy sources has also increased. Bio-fuels such as ethanol have attractive prospects in the industry. Ethanol can be produced using a series of pathways.

Figure 1 from Wei et al, 2008 shows the different pathways that can be used for ethanol production from feedstock.For the purpose of this study the main focus will be on the gasification biosynthesis pathway used by the bacterium Clostridium ljungdahlii

Next Page

Homepage

1.Background2.Executive Summary3.Introduction4.Summary

4.1 Article 4.2 Article 5. Comparative Analysis6. References

Page 6: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

3. IntroductionCarbon monoxide is highly toxic to living creatures with the exception

of microorganisms such as acetogenic bacteria. These can use carbon

monoxide as a carbon source and synthesise ethanol and acetate

together with some other products (Kopeke et al., 2011). The

metabolic pathway used by these microorganisms is known as the

Wood-Ljungdahl pathway (shown in figure 1). The fermentation process

has a number of advantages though syngas fermentation is yet to be

used on a commercial scale. The advantages include the utilization of

the whole biomass for product formation; no pre-treatment steps

required; high specificity of biological catalysts (Munasinghe and

Khanal,2010). Nevertheless, there are also some challenges involved in

the process one of which is the poor solubility of carbon monoxide gas

in aqueous solutions (Abubackar et al., 2012)

For the purpose of this study, the activity of two Clostridium species

grown under different conditions for the optimisation of ethanol

production were compared.

Previous Next

Homepage

1.Background2.Executive Summary3.Introduction4.Summary

4.1 Article 14.2 Article 2

5. Comparative Analysis6. References

Page 7: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

3. Introduction

Figure 1 adapted from Kopke et al, 2011

The Wood-Ljungdahl Pathway-Conversion of carbon monoxide to ethanol

Page 8: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

4.1 Summary

Overview

C.ljungdahlii is an acetogenic bacteria, which, when grown on carbon monoxide produces ethanol and acetate as the

main end-products. Optimisation of ethanol production requires a shift in metabolism from acetogenesis (Acetic acid

formation) to solventogenesis (ethanol production). Resting cells have to found capable of inducing this shift in

metabolism and also increase cell stability. In this study, the ability of nitrogen-limited media to initiate a non-growing

in C.ljungdahlii and the effects of different growth states and medium pH on ethanol and acetate production were

examined.

Materials and Methods

Table 1 (Cotter et al, 2009) shows the

types of media used for C.ljungdahlii.

Three types of non-growth media

were prepared anaerobically.

The cultures were initially grown until

a mid-late log phase and then were

subjected to a series of centrifugation

and resuspension. The suspensions

were then transferred to the

appropriate non-growth media.

(material used from Cotter et al.,2009)

Ethanol and acetate production by Clostridium ljungdahlii and Clostridium autoethanogenum using resting cellsJacqueline L. Cotter , Mari S. Chinn and Amy M.Grunden

(*note for the purpose of this study the main focus will be on Clostridium ljungdahlii)

Non-growth media

Page 9: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

4.1 Summary

Effect of non- growth media

Studies showed that the addition of vitamins, salts

and trace elements enabled the cultures to maintain high

cell densities in nitrogen deficient media. The results from

figure 1 showed that relatively few cultures from each type

of non-growth media remained viable. The ethanol

production levels were affected by the media type used.

Effect of pH on resting cell performance

It was found that lowering pH values did not affect the

stability of the culture but had an adverse effect on the

viability.

Discussion

The results obtained in this study are quite different

from studies carried out in the past whereby, ethanol

is a secondary metabolite in syngas fermentation. A shift

in metabolism as observed with other studies was not

successfully established in this experiment.

(Materials used from Cotter et al., 2009)

Results and Discussion

Figure 1 shows the metabolism of C.ljungdahlii – ethanol production over time in initial non-growth media

Figure 2 shows the metabolism of C.ljungdahlii on NG.RCM.NA.SVE medium-ethanol production over time at different pH

Homepage

1.Background2.Execuve Summary3.Introduction4.Summary 4.1 Article 1 4.2 Article 25. Comparative Analysis

6. References

Page 10: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

4.2 Summary

Overview

Second generation biofuels such as ethanol by syngas fermentation using C.ljungdahlii

represents several challenges, one of which is the cultivation of the bacterium as it is strictly

anaerobic. The main aims of this study were to investigate and monitor the fermentation

conditions such as fresh medium flow rate, culture pH on cell concentration and viability,

substrate uptake and product formation during the continuous cultivation of C.ljungdahlii.

(*note for the purpose of this study only the results for substrate uptake and product formation

will be used)

Materials and methods

The inoculum was prepared using a defined medium containing,

NaHCO3, a reducing agent, vitamins, trace elements. The pH

of the medium was maintained at 6.8 using NaOH solution.

The bioreactor was operated under batch conditions for 3 days

following which a continuous mode was started with a liquid

flow rate of 0.25mL/min.

(note pH of bioreactor was not controlled)

Cell growth was monitored by determining

the cell dry weight of C.ljungdahlii and

acetate and ethanol production was

monitored using a gas chromatogram.

(Material used from Mohammadi et al., 2012)

Sustainable ethanol fermentation from synthesis gas by Clostridium ljungdahlii in a continuous stirred tank bioreactorMohammadi M., Younesi H., Najafpour G., Mohamed A.R.

Figure 1 shows the operating conditions of the bioreactor for optimising the liquid flow rate at a constant stirring rate of 500 rpm and a gas flow rate of 14mL/min

1.Background2.Executive Summary

3.Introduction4.Summary 4.1 Article 1 4.2 Article 25. Comparative Analysis6. References

Homepage

Page 11: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

4.2 summary

The results for substrate uptake, product formation and varying pH were analysed.Effect of varying pH

The effect of changes in pH can be seen in Figure 2,whereby a drastic

reduction in cell density was observed due to a drop in pH to 4.18.

A re-adjustment in pH to 6.5 allowed to cells to recover within 5 days.

Product formation

From figure 3, it was observed that over the first 7 days when there was

a drop in the pH of the culture, acetate was the main product. Following this,

a drastic increase in both ethanol and acetate was observed, with the

product levels reaching a peak of 9g/L on the 10th day of the experiment.

Discussion

A decrease in pH affects the cell stability and product formation.

The production of acetate during the first 7 days led to a decrease in external pH and loss of constant

internal pH. Acetate- a weak organic acid, can accumulate inside the cells

and in the presence of H+ ions cause a decrease in internal pH. This in turn

leads a metabolic shift from acetogenesis to solventogenesis.

Hence , ethanol production occurred after a decrease in internal pH.

This study was successful in demonstrating a shift in the

metabolic pathway of C.ljungdahlii . Further studies involving

variation of other parameters are expected to help in increasing

the molar ratio of ethanol to acetate.

(Materials used from Mohammadi et al., 2012)

Results and Discussion

Figure 2 shows the change in the cell dry weight with changes in pH over time

Figure 3 shows the varying levels ethanol and acetate produced over time

Page 12: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

5. Comparative analysis

The works from both Cotter et al. and Mohammadi et al. focused on the

production of ethanol from syngas fermentation using the bacterium Clostridium

ljungdahlii .

The studies performed in Cotter et al. were relatively complex and the goals of

the experiments performed for C.ljungdahlii were not successfully met with. The

results obtained showed were different to what was expected-ethanol was

produced in the growth phase of the bacteria while the results obtained from

other researchers showed otherwise.

The work performed by Mohammadi et al. aimed at providing a better

understanding and correlation of the biochemical pathway used by C.ljungdahlii.

The design of the experiment was far much simpler than the work that was

undertaken by Cotter et al. .

The goals of the experiment were successfully met with through the

demonstration of a shift in metabolism of the bacteria under different

parameters. The shift in metabolism from the acetogenic pathway to the

solventogenic pathway was found to correlate well with the Wood-Ljungdahl

Pathway. Furthermore , the metabolic shift was also observed in a study

performed by Gaddy et al.

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1.Background2.Executive Summary

3.Introduction4.Summary 4.1 Article 1 4.2 Article 25. Comparative Analysis6. References

Page 13: Biofuel Production from Carbon monoxide. Homepage 1.Background 2.Executive Summary 3.Introduction 2.Executive Summary 3.Introduction 4.Summary 4.1 Article

6. References1) Abubackar H.N., Veiga M.C., Kennes C., 2012. “Biological conversion of carbon

monoxide to ethanol: Effect of pH, gas pressure, reducing agent and yeast extract”,

Bioresource Technology 114:518-522

2) Cotter J.L., Chinn M.S., Grunden A.M., 2009. “Ethanol and acetate production by

Clostridium ljungdahlii and Clostridium autoethanogenum using resting cells”,

Bioprocess and Biosystems Engineering 32(3):369-380

3) Kopke M., Mihalcea C., Bromley J.C., Simpson S.D., 2011. “Fermentative

production of ethanol from carbon monoxide” Current Opinion in Biotechnology

(22)3:320-325

4)Mohammadi M., Younesi H., Najafpour G., Mohamed A.R., 2012. “Sustainable

ethanol fermentation from synthesis gas by Clostridium ljungdahlii in a continuous

stirred tank bioreactor” Journal of Chemical Technology and Biotechnology

(87)6:837-843

5)Munasinghe P.C., and Khanal S.K.,2010. “Biomass-derived syngas fermentation

into biofuels: Opportunities and challenges” Bioresource Technology (101):13 5013-

5022

6) Wei L., Pordesimo L.O., Igathinathane C., Batchelor W.D.,2008. “Process

engineering evaluation of ethanol production from wood through bioprocessing and

chemical catalysis” Biomass and Bioenergy 33:255-266

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