Yeast Extract as an Effective and Safe Mediator for the Baker's-Yeast

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Yeast Extract as Effective and Safe Mediator for the Baker's Yeast-Based Microbial fuel Cell Enas Taha Sayed, Nasser A. M. Barakat, Mohammad Ali Abdelkareem, H Fouad, and Nobuyoshi Nakagawa Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/ie5042325 • Publication Date (Web): 10 Mar 2015 Downloaded from http://pubs.acs.org on March 15, 2015

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Industrial & Engineering Chemistry Research

Yeast Extract as Effective and Safe Mediator for the

1

Baker's Yeast-Based Microbial fuel Cell

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Enas Taha Sayed1*, Nasser A. M. Barakat1,2*, Mohammad Ali Abdelkareem1, H. Fouad3,4, and Nobuyoshi Nakagawa5

10 11

1

12 13

2

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Department of Chemical Engineering, Faculty of Engineering, Minia University, Egypt

Department of Organic Materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756, Republic of Korea 3

Applied Medical Science Department, RCC, King Saud University, P.O. Box 800, Riyadh

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11421, Saudi Arabia 4

Biomedical Engineering Department, Faculty of Engineering, Helwan University, P. O. Box

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11792, Helwan, Egypt 5

Gunma University, Graduate school of Engineering, Chemical and Environmental

19

Engineering, Kiyu, Gunma, Japan

20 21 22 23 24 25 26

Corresponding authors:

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Nasser A.M. Barakat,

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Tel: +82632702363, Fax: +82632704249

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E-mail: [email protected]

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Enas Taha Sayed

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E-mail: [email protected]

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Abstract

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Although utilizing the exogenous mediators distinctly enhances the microbial fuel cell

3

(MFC) performance, possibility of microorganisms’ toxicity, environmental aspect and

4

cost are the main dilemmas facing wide applications. Therefore, successful applying of

5

the Yeast Extract as a mediator in the Baker’s yeast, Saccharomyces cerevisiae,-based

6

MFCs would be of great interest as it will overcome all the aforementioned problems.

7

The influence of the Yeast Extract addition was investigated based on the yeast cell

8

adhesion on the surface of plain and gold-sputtered carbon papers anodes. In case of

9

plain carbon paper, the addition of the Yeast Extract considerably enhanced the

10

performance of the yeast-based MFC which can be attributed to the Yeast Extract role as

11

growth media and/or as a mediator; the current and power densities increased from 94 to

12

190 mA/cm2 and from 12.9 to 32.6 mW/cm2, respectively. However, compared to the

13

plain carbon paper, in case of gold-sputtered anode the performance significantly

14

increased with Yeast Extract addition while it drastically decreased without Yeast

15

Extract; the current and power densities increased from 25 to 300 mA/cm2 and from 2 to

16

70 mW/cm2, respectively. The obtained results indicated that Yeast Extract can be

17

exploited as an effective mediator in the Saccharomyces cerevisiae-based MFCs.

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Keywords: Microbial fuel cell; Baker’s yeast; Saccharomyces cerevisiae; Mediator; Yeast Extract.

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1. Introduction

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Microbial fuel cell (MFC) is an electrochemical device that can directly convert

4

the chemical energy of the organic compounds into electricity using the catalytic activity

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of living microorganisms in oxidizing of the organic materials 1. The MFC consists of

6

two electrodes, an anode and a cathode, separated by an electrolyte. At the anode,

7

microorganisms oxidize the organic compounds under anaerobic conditions. These

8

microorganisms pass electrons to an electrode which acts as an electron acceptor. The

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mechanisms of the electron transfer in the MFCs can be divided into direct and indirect

10

electron transfer. Direct electron transfer takes place through the outer membrane

11

cytochrome

12

However, there is indirect electron transfer can take place with the help of an electron

13

mediator, in such a case the efficiency distinctly enhanced. The mediators can be

14

self-mediators (produced by the microorganism) or an externally added mediator;

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exogenous mediator. Beside the scarcity as not all microorganisms are able to produce

16

self-mediators, the exogenous mediators usually improve the rate of electron transfer

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higher than the self-ones. However, addition of exogenous mediators is not preferable as

18

they are usually expensive, sometimes environmentally unacceptable, and generally toxic

19

to the microorganism at high concentrations 13-15. Therefore, biologically safe, cheap and

2-10

, nanowires11 or trans-membrane electron transport proteins


12, 13

,


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efficient exogenous mediators would be strongly feasible from the technical point of

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view.

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Among the reported microorganisms for the MFC, Baker's yeast (Saccharomyces

4

cerevisiae) has many attractive features including nonpathogenic, inexpensive, easy mass

5

cultivation, and can be maintained for a long time in the dried state. Recently, it was

6

reported that the electron transfer in the yeast-based MFC was dominated through the

7

surface confined species, so the adhesion of the yeast on the electrode is responsible for

8

electron transfer, and also no role of the endogenous mediator (if present) in the electron

9

transfer

16,17

. Accordingly, the performance of a mediator-less baker's yeast-based MFC

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is not enough for practical use and addition of exogenous mediator is required for

11

improving the performance.

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Yeast Extract is the common name for various forms of processed yeast products

13

made by extracting the cell contents (removing the cell walls); they are used as food

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additives, flavorings, and nutrients for bacterial culture media. Yeast Extract is one of the

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most important components for microbial growth media and it was widely used in MFC

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as growth media. Masuda et al., revealed that riboflavin and other flavin-type compounds,

17

using a HPLC system and CV measurements, contained in Yeast Extract18. Moreover,

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they proved that the flavin contained in Yeast Extract works as an exogenous mediator

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for fermentative bacterium Lactococcus lactis while it was not electrochemically active 4 ACS Paragon Plus Environment

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for other types of microorganisms, such as Escherichia coli and Propionibacterium

2

freudenreichii.

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According to their study, not all the microorganisms have the ability to exploit

4

flavin for extracellular electron transfer even though they can produce and secrete flavin

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compounds. Therefore, the determination of the type of the microorganisms having the

6

capability for flavin utilization is of a great importance in the MFCs applications.

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Yeast Extract is commonly used in MFC as growth media without considering its

8

role as mediator. Based on the results of Masuda et al., the effect of Yeast Extract as

9

mediator must be investigated to clear its role as nutrient as well as mediator or not.

10

Usually Yeast Extract is used as nutrient in yeast based MFC, and based on the

11

results of Masuda et.al., its role as mediator or not in this type of MFC has to be clarified.

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The success in applying the Yeast Extract as a mediator for yeast-based MFC will

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avoid the problem of the toxic effect of the mediator which is the biggest challenge

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facing the application of the exogenous mediators, moreover it is environmentally safe

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and cheap. According to our best knowledge, no previous reports in the literature about

16

using Yeast Extract as a mediator for yeast-based MFC have been introduced.

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In this study, investigation of influence of utilizing the dry powder Yeast Extract as

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a mediator in yeast-based MFC was performed. The effect of the dry powder Yeast

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Extract on the open circuit voltage (OCV), anode potential and the power generation 5 ACS Paragon Plus Environment


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have been investigated. Typically, the performance of a yeast-based MFC having an a

2

gold-sputtered anode has been investigated with and without Yeast Extract addition. The

3

gold-sputtered anode has been used to exploit the antibacterial effect of gold in inhibition

4

of the growth of the yeast cells. Actually, according to our previous study

5

confirmed that the modification of carbon paper anode with a thin nano layer of gold

6

inhibited the growth of the yeast cells on the anode surface and consequently the

7

performance drastically decreased. The results of the present study indicated that the

8

Yeast Extract strongly enhances the performance of the yeast-based MFC as it can be

9

used as a mediator as well as an accelerator of the growth rate.

17

, it was

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2. Materials and methods 2.1 Sputtering of Au on the carbon paper

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A gold-sputtered anode was prepared by sputtering of gold on the surface of the

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anode carbon paper. Au was sputtered on the surface of carbon paper (2.2×2.2 cm2,

15

EC-20-10, Electro Chem, Inc.) with a sputtering machine (JOEL JFC-2300 HR high

16

resolution fine coater) using Au (99.99%) disk as a target. The sputtering was conducted

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under 0.02 mbar of Ar gas with the power of 80 W for a certain time based on a

18

calibration curve.

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2.2 Membrane electrode assembly (MEA) preparation and cell structure

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A carbon paper with Pt(1 mg/cm2)/C catalyst (2.2×2.2 cm2, EC-20-10, Electro

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Chem, Inc.) was used as cathode. A carbon paper with and without sputtered metal was

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used as the anode. Nafion 117 was used as the electrolyte membrane after pre-treatment.

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The cathode and the membrane were hot-pressed at 135 oC and 5 MPa for 3 min. The

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anode and membrane with cathode were sandwiched between two stainless steel current

7

collectors (1.0 mm thickness with open holes). Figure 1 shows a schematic diagram of

8

the used fuel cell structure. The cell was an open-air cathode type. The anode chamber

9

had a volume of 84 cm3. A reference electrode, Ag/AgCl, was installed in the anode

10

chamber. The current density was calculated based on the effective anode area; 4 cm2.

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2.3 Yeast and anolyte preparation

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Saccharomyces cerevisiae (Baker’s yeast, S.I.L esaffre 59703 Marcq France)

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was used as a biocatalyst. A 0.13 g sample of the dried yeast was cultivated for 16 h at 30

14

o

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2 g peptone (Becton, Dickinson and Co.), 1 g malt extract (MP Biomedical, LLC) and 1

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g Yeast Extract (Nihon Pharmaceutical Co., Ltd.). A 10 ml aliquot of the cultivated

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medium mixed with 0.35 g peptone and 1.4 g glucose was used as the anolyte. Yeast

18

Extract, 1.4 g, was added and the anolyte volume was completed to 70 ml using 60 ml of

19

50 mM phosphate buffer. The pH of the anolyte was adjusted to 7.0.

C in 100 ml of distilled water containing 0.5 g glucose (Wako Pure Chemical Ind., Ltd.),



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2.4 Cell operation and electrochemical measurements

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The anolyte, 70 ml, was injected into the anode chamber and then the

3

measurements were started after purging the anolyte with gaseous nitrogen for 30 min.

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The microbial fuel cell was operated at 35 oC. The electrode potentials versus the

5

reference electrode (Ag/AgCl) as well as the OCV were recorded with time until they

6

became stable. All the voltage and potential mentioned in the text and/or on the graphs

7

was changed versus NHE pH7 (vs. NHE pH7). The cell circuit was then closed and the

8

current-electrode potential characteristics were measured from OCV to zero voltage at a

9

scan rate of 1 mV/s. The current density at a constant cell voltage of 0.2 V was then

10

measured. These electrochemical measurements were carried out for the fuel cell with the

11

different anodes by an electrochemical measurement system (HAG-5010, Hokuto Denko,

12

Co., Ltd.). cyclic voltammetry of the Yeast Extract has been carried out in three electrode

13

cell structure using glassy carbon electrode, Diameter 3mm, reference electrode Ag/AgCl,

14

and counter electrode, Pt wire. In-situ cyclic voltammetry was carried out using different

15

YE concentrations, 0.1, 1, 10 and 100 g L−1 YE from −0.4 to 0.8 V vs. normal hydrogen

16

electrode (NHE pH 7) at the scan rate 10 mV s−1 using the anode as working electrode,

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cathode as counter electrode and Ag/AgCl as reference electrode.

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2.5 Characterization of the different anode materials

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SEM observations of the different anodes were conducted before and after the

3

experiments using a scanning electron microscope (Hitachi, Miniscope TM-1000). After

4

the experiments, the utilized anodes were dried at 50 oC for about 1 h before SEM

5

observation.

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3. Results

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3.1 Effect of Yeast Extract addition on the performance of yeast-based MFC using plain

9

carbon paper as anode

10

Figure 2 shows the OCVs and the anode potentials with time for yeast-based

11

MFC with and without Yeast Extract addition using plain carbon paper as anode. As

12

shown in the figure, without Yeast Extract addition, the OCV started from 0.3 V and

13

gradually increased with time until reached the steady value (0.66 V) after 22 h. The

14

anode potential started from 0.45 V (vs. NHE pH7) and gradually decreased until reached

15

to the steady value (0.05 V vs. NHE pH7) within 22 h. On the other hand, in case of

16

Yeast Extract addition, the OCV started from 0.53 V and reached to the steady value,

17

0.76 V, after 13 h. Moreover, the anode potential started from 0.2 V (vs. NHE pH7) and

18

decreased until reached to the steady value of -0.15 V (vs. NHE pH7) within 13 h in both

19

cases. It is noteworthy mentioning that the increase in the OCV would be related to the



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decrease in the anode potential. Therefore, it can be observed that addition of the Yeast

2

Extract led to decrease the initial anode potential from 0.45 to 0.2 V (vs. NHE pH7) and

3

decrease the final anode potential from 0.05 to -0.14 V (vs. NHE pH7) as well as

4

decrease the time to reach the steady anode potential value from 22 to 13 h.

5

Figure 3 shows the effect of the Yeast Extract addition on the electrode

6

potentials (Fig. 3a), and the current-voltage and current-power curves (Fig. 3b) of the

7

yeast-based MFC. As shown, the maximum current and power densities significantly

8

increased due to addition of the Yeast Extract. Typically, the maximum current density

9

increased from 94 to 190 mA/m2 and the maximum power densities increased from 12.9

10

to 32.6 mW/m2, these results scientifically emphasize the positive effect of Yeast Extract

11

addition.

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Figure 4 displays the effect of Yeast Extract on the i-t performance at 0.2 V of the

13

yeast-based MFC. As shown, in case of Yeast Extract-free MFC, the initial current

14

density was around 60 mA/m2 then rapidly decreased and reached to a stable value of ~ 6

15

mA/m2 within 0.5 h. On the other hand, in case of the Yeast Extract addition, the initial

16

current density was ~ 220 mA/m2 then rapidly decreased and reached to a stable value of

17

~110 mA/m2 within 1.5 h. The stable current density for more than 4h indicated the good

18

stability of the yeast cells adhesion on the anode surface. The decrease in the initial

19

current density in both cases would be related to the depletion of the electrons 10 ACS Paragon Plus Environment

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accumulated under the OCV conditions. This figure clearly demonstrates the significant

2

effect of the Yeast Extract addition as the stable current density increased more than 17

3

times. The columbic efficiency (CE) could be calculated using the following

4

equation19-21:

5

CE (%) = (CEx/CTh)

6

Where CEx is the total coulombs calculated by the integration of the area under the i-t

7

curve, i.e., CEx = ‫׬‬௜ୀ଴ ݅ ∗ ‫ݐ‬

8

the number of moles of electrons produced per mole substrate, M is the concentration,

9

and v is the liquid volume. According to the above equation, the CE will be directly

10

proportional to the current density. Where the current density increased during the i-t

11

measurements, Fig. 4, more than 17 times, therefore the CE will be increased 17 times.

12

The constant discharge of current with time indicated that the yeast cells have good

13

stability on the anode surface.

௜

and the CTh = FbMv where, F is the Faraday constant, b is

14

Figure 5 displays the SEM images of the utilized carbon paper anodes. As

15

shown in Fig. 5A which demonstrates the utilized anode after finishing the experiment in

16

case of Yeast Extract-free MFC, the attached yeast is good. However, as shown in Fig.

17

5B, the observed attached yeasts distinctly increased in a case of utilizing Yeast Extract.

18



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3.2 Effect of Yeast Extract addition on the performance of yeast based MFC using

2

gold-sputtered carbon paper as anode

3

To properly understand the real influence of the Yeast Extract, the yeast growth 17

4

should be annihilated. From our previous study

, we have confirmed that the

5

modification of the anode surface, carbon paper, with a thin nanolayer of the gold

6

inhibits the growth of the yeast cell on the anode surface so the corresponding cell

7

performance will be very low. Figure 6 shows the OCVs and the anode potentials with

8

time for yeast-based MFC with and without Yeast Extract addition using gold-sputtered

9

carbon paper as anode. As shown in Fig. 6, without Yeast Extract addition, the OCV

10

slightly increased after 5 h then rapidly decreased again and remain constant at 0.45V.

11

While in case of the Yeast Extract addition, the OCV gradually increased from 0.5 to

12

0.91 V within 8 h then became constant. These variations in the OCV were in

13

consequence with the variation in the anode potentials. Where in case of no Yeast Extract

14

addition, the anode potential was nearly constant, therefore the OCV becomes constant.

15

While in case of the Yeast Extract addition, the anode potential decreased from 0.25 to

16

-0.15 V (vs NHE pH7).

17

Figure 7 shows the effect of the Yeast Extract addition on the electrode potentials (Fig.

18

7a) and the current-voltage and current- power curves (Fig. 7b) of the yeast-based MFC

19

using gold-sputtered carbon paper as anode. As shown in the figure, addition of the Yeast


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Extract led to increase the maximum current density from 25 to 300 mA/m2 and the

2

maximum power density from 2 to 70 mW/m2.

3

Fig. 8 displays the SEM image of the gold-sputtered anode after utilizing in the MFC, as

4

shown in the figure no attached cells can be observed which affirms our conclusion about

5

the influence of gold on stopping the yeast growth. Fig. 9 shows the In-situ cyclic

6

voltammetry using different YE concentrations, 1 to 100 g L−1 YE from −0.4 to 0.8 V vs.

7

NHE pH7 at the scan rate 10 mV s−1.

8 9

4. Discussion

10

The common role of the Yeast Extract in improving the performance of baker's

11

yeast-based MFC would be related to its role as a growth media. Therefore, in the plain

12

carbon paper-based anode, the observed good performance can be related to increasing

13

cell growth rate which can be observed in the SEM image shown in Fig. 5. Accordingly,

14

it can be supposed that the electron transfer in case of utilizing the plain carbon anode

15

yeast-based MFC was done by the direct contact. Therefore, increase in the yeast cell

16

adhesion on the anode surface resulted in increase the electron transfer and subsequently

17

enhances the power generation which supports the hypothesis about electrons transfer by

18

the direct contact strategy.



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As aforementioned in the introduction section, it was reported that the Yeast 18

2

Extract contains an intrinsic mediator, possibly a flavin-type compound

. Therefore,

3

another explanation for the improved performance in case of utilizing the Yeast Extract

4

in this study is that the baker's yeast uses the flavin-type compound contained in Yeast

5

Extract as a mediator. In other words, the addition of the Yeast Extract increases the

6

electron transfer by incorporating the yeast cells in the bulk solution as well as that

7

adhered to the anode surface. Overall, one can claim that the Yeast Extract could

8

improve the performance of baker's yeast-based MFC by enhancing the growth media

9

and/or serving as a mediator.

10

The role of the Yeast Extract as a mediator in the yeast-based MFC can be easily

11

investigated in the case of the gold-sputtered anode as the direct electron transfer would

12

be avoided and thus the role of Yeast Extract as a mediator could be easily investigated.

13

Therefore, in case of utilizing gold-sputtered carbon paper anode, the observed

14

drastically decrease in the performance in case of Yeast Extract-free cell (Fig. 7) would

15

be related to the inhibition of the yeast cell growth on the gold-sputtered surface 17 which

16

could be scientifically proved in Fig. 8B. Moreover in case of Yeast Extract-free MFC,

17

compared to the plain anode surface (Fig. 3b), the performance of the gold-sputtered

18

anode drastically decreased the power and current densities from 12.9 to 2 mW/m2, and


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from 94 to 25 mA/m2, respectively this is clearly related to the antibacterial effect of the

2

gold22-26.

3

On the other hand in case of Yeast Extract-containing cells, the maximum power and

4

current densities upon gold-sputtered of the anode increased from 32.6 to 70 mW/m2, and

5

from 190 to 300 mA/m2, respectively. The significant increase in the performance

6

confidently proves the role of the Yeast Extract as a mediator without ignoring its effect

7

on the metabolism which could contribute in the cell performance. In other words, it can

8

be claimed that the electron transfer takes place from the yeast cells in the bulk solution

9

to the anode surface via the mediator existed in the Yeast Extract. Interestingly, the

10

obtained anode potential of -0.15V is very close to that of the flavin; -0.2 V (vs. NHE

11

pH7)18 . It is noteworthy mentioning that the decrease in the time required for reaching

12

the steady state anode potential (from 15 to 8 h) and the increase in the performance

13

would be related to the increase in the electron conductivity of the anode surface through

14

the sputtered gold layer 27. Table 1 summarizes the utilized cells performances.

15

Fig.9 shows the cyclic voltammogram using different Yeast Extract

16

concentration, 0.1, 1, 10, and 100 g L−1.

17

pH7, a reduction peak can be clearly seen especially at high concentrations. This

18

reduction peak in accordance with that reported with Masuda et al. would be related to

As shown in the figure, at −0.2 V vs. NHE



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1

the riboflavin contained in the Yeast Extract which further supports the results of the

2

present study.

3 4

5. Conclusion

5

Overall, the present study can draw the following conclusion: Yeast Extract as

6

cheap, biologically safe and non toxic material at any concentration can be utilized as an

7

effective exogenous mediator for the Baker’s yeast (Saccharomyces cerevisiae)-based

8

microbial fuel cells. Beside the known role in modification of the growth rate as it is

9

utilized as nutrient, Yeast Extract can serve in electrons transfer process from the bulk to

10

a yeast-free carbon paper anode which confirms the ability of exploiting this cheap and

11

biologically safe material as mediator. Moreover and interestingly, the corresponding

12

anode potential in case of Yeast Extract addition is -0.15 V (vs. NHE pH7) which is very

13

close to the widely utilized and expensive mediator; flavin. Overall, this study opens a

14

new avenue for the Yeast Extract to be exploited as mediators in the yeast-based MFCs.

15

Author Contributions

16

The manuscript was written through contributions of all authors. All authors have given

17

approval to the final version of the manuscript.

18

Notes

19

The authors declare no competing financial interest


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1

Acknowledgement

2 3 4

The authors would like to extend their sincere appreciation to the Deanship of Scientific Research at king Saud University for its funding this research group NO. (RG -1435-0052).

5 6 7 8

References

9

1. Min, B., Logan, B.E., Continuous electricity generation from domestic wastewater

10 11

and organic substrates in a flat plate microbial fuel cell, Environ. Sci. Technol. (2004), 38, 5809–5814.

12 13 14 15

2. Shukla1, A. K., Suresh, P., Berchmans1, S., Rajendran1, A., Biological fuel cells and their applications, Current Science (2004), 87, 455-468. 3. Kim, H.J., Park, H.S., Hyun, M.S., Chang, I.S., Kim, M., Kim, B.H., A mediator-less microbial fuel cell using a metal reducing bacterium, Shewanella putrefaciense,

16 17 18

Enzyme Microb. Technol. (2002), 30, 145–152. 4. Kim, B.H., Kim, H.J., Hyun, M.S., Park, D.H., Direct electrode reaction of Fe(III) reducing bacterium, Shewanella putrefaciens. J. Microbiol. Biotechnol. (1999), 9,

19 20 21 22 23 24 25 26

127– 131. 5. Ringeisen, B.R., Ray, R., Little, B., A miniature microbial fuel cell operating with an aerobic anode chamber. J. Power Sources (2007), 165, 591–597. 6. Bond, D.R., Lovley, D.R., Electricity production by Geobacter sulfurreducens attached to electrodes. Science (2002), 295, 483–485. 7. Pham, C.A., Jung, S.J., Phung, N.T., Lee, J., Chang, I.S., Kim, B.H., Yi, H., Chen, J., A novel electrochemically active and Fe(III)-reducing bacterium phylogenetically related to Aeromonas hydrophila isolated from a microbial fuel cell. FEMS

27 28 29

Microbiol. Lett. (2003), 223, 129–134. 8. Chaudhuri, S.K., Lovley, D.R., Electricity generation by direct oxidation of glucose in mediatorless microbial fuel cells. Nat. Biotechnol. (2003) 21, 1229–1232.

30 31 32

9. Zhang, T., Cui, C., Chen, S., Ai, X., Yang, H., Shen, P., Peng, Z., A novel mediatorless microbial fuel cell based on direct biocatalysis of Escherichia coli. Chem. Commun. (2006) 2257–2259.

33 34 35

10. Zhang, T., Zeng, Y., Chen, S., Ai, X., Yang, H., Improved performances of E. coli-catalyzed microbial fuel cells with composite graphite/PTFE anodes. Electrochem. Commun. (2007), 9, 349–353.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2

11. Reguera, G., McCarthy, K.D., Mehta, T., Nicoll, J.S., Tuominen, M.T., Lovley, D.R. Extracellular electron transfer via microbial nanowires, Nature (2005), 435,

3 4 5

1098–1101. 12. Schaetzle, O., Barrie`re, F., Baronian, K., Bacteria and yeasts as catalysts in microbial fuel cells: electron transfer from micro-organisms to electrodes for green

6 7

electricity. Energy Environ. Sci. (2008), 1, 607–620. 13. Prasad, D., Arun, S., Murugesan, M., Padmanaban, S., Satyanarayanan, R.S.,

8 9 10 11

Berchmans, S., Yegnaraman, V., Direct electron transfer with yeast cells and construction of a mediatorless microbial fuel cell, Biosensors and Bioelectronics (2007), 22, 2604–2610. 14. Hubenova, Y., Mitov, M., Potential application of Candida melibiosica in biofuel

12 13 14 15 16

cells, Bioelectrochemistry (2010), 78, 57–61. 15. Gil, G.C., Chang, I.S., Kim, B.H., Kim, M., Jang, J. K., Park, H. S., Kim, H. J., Operational parameters affecting the performance of a mediator-less microbial fuel cell. Biosens. Bioelectron. (2003), 18, 327-334. 16. Sayed, E., Tsujiguchi, T., Nakagawa, N., Catalytic Activity of Baker’s Yeast in a

17 18 19

Mediatorless Microbial fuel Cell, Bioelectrochemistry (2012), 86, 97–101. 17. Sayed, E., Tsujiguchi, T., Nakagawa, N., effect of metal modification to carbon paper anodes on the performance of yeast-based microbial fuel cell Part I: In case

20 21 22 23

without exogenous mediator, Key Engineering Materials (2013), 534, 76-81. 18. Masuda, M., Freguia, S., Wang, Y., Tsujimura, S., Kano, K., Flavin contained in yeast extract are exploited for anodic electron transfer by Lactococcus lactis, Bioelectrochemistry (2010), 78, 173-175.

24 25 26

19. Abdelkareem, M. A., Nakagawa, N., DMFC employing a porous plate for an efficient operation at high methanol concentrations, J. Power Sources, (2006), 162, 114-123.

27 28 29

20. Abdelkareem, M. A., Morohashi, N., Nakagawa, N., Factors affecting methanol transport in a passive DMFC employing a porous carbon plate, J. Power Source (2007) 172, 659-665.

30 31 32 33 34 35 36

21. Kim, J. R., Min, B., Logan, B.E., Evaluation of procedures to acclimate a microbial fuel cell for electricity production, Appl Microbiol Biotechnol, (2005), 68, 23–30. 22. Hernández-Sierra, J. F.; Ruiz, F.; Cruz Pena, D. C.; Martínez-Gutiérrez, F.; Martínez, A. E.; de Jesús Pozos Guillén, A.; Tapia-Pérez, H.; Martínez Castañón, G., The antimicrobial sensitivity of Streptococcus mutans to nanoparticles of silver, zinc oxide, and gold. Nanomedicine: Nanotechnology, Biology and Medicine 2008, 4, 237-240.


Page 18 of 31

Page 19 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1 2

23. Mubarak Ali, D.; Thajuddin, N.; Jeganathan, K.; Gunasekaran, M., Plant extract mediated synthesis of silver and gold nanoparticles and its antibacterial activity

3 4 5

against clinically isolated pathogens. Colloids and Surfaces B: Biointerfaces 2011, 85, 360-365. 24. Karamushka, V. I.; Gadd, G. M., Interaction of Saccharomyces cerevisiae with gold:

6 7

toxicity and accumulation. BioMetals 1999, 12, 289-294. 25. Mourato, A.; Gadanho, M.; Lino, A. R.; Tenreiro, R., Biosynthesis of crystalline

8 9 10 11

silver and gold nanoparticles by extremophilic yeasts. Bioinorganic chemistry and applications 2011, 2011. 26. Smith, M. R.; Boenzli, M. G.; Hindagolla, V.; Ding, J.; Miller, J. M.; Hutchison, J. E.; Greenwood, J. A.; Abeliovich, H.; Bakalinsky, A. T., Identification of gold

12 13 14 15 16

nanoparticle-resistant mutants of Saccharomyces cerevisiae suggests a role for respiratory metabolism in mediating toxicity. Appl. Environ. Microbiol. 2013, 79, 728-733. 27. Sayed, E., Tsujiguchi, T., Nakagawa, N., effect of metal modification to carbon paper anodes on the performance of yeast-based microbial fuel cell Part II: In case

17 18

with exogenous mediator, methylene blue, Key Engineering Materials (2013), 534, 82-87.

19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3 4 5 6 7 8 9 10 11

Figures captions

12

Figure 1

13

1-Cover plates

14

4- Anode (modified face facing the solution)

A schematic diagram of the cell structure

15 16

21

without Yeast Extract (YE) using plain carbon paper as anode. Figure 3 The effect of the Yeast Extract (YE) addition using non modified carbon paper as anode on: (a) The electrode potentials, (b) The current-voltage and current- power curves. Figure 4 Effect of the Yeast Extract addition on the current discharge at 0.2 V in case of non

22 23

modified anode

Figure 5 SEM images for the utilized plain carbon paper anodes after the experiments in

24 25 26 27 28 29

5- Membrane and cathode

Figure 2 OCVs and the anode potentials with time for yeast- based MFC with and

19 20

3- Current collectors

6. Reference electrode position

17 18

2- Anode chamber

case of Yeast Extract –free; (a) and –containing; (b) MFC. Figure 6

The OCVs and the anode potentials with time for yeast- based MFC with and without Yeast Extract using gold-sputtered carbon paper as anode.

Figure 7 The effect of the Yeast Extract addition in case of gold-sputtered carbon paper as anode on: (a) The electrode potentials, (b) The current-voltage and current- power curves.


Page 20 of 31

Page 21 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


1

Figure 8 SEM images for the utilized gold-sputtered carbon paper anodes before; (a) and

2

after; (b) the experiments in case of Yeast Extract–containing MFC.

3

Figure 9 In-situ voltammograms of the YE with different concentrations, 0.1, 1, 10 and

4

100 g L−1 YE at the scan rate 10 mV s−1.

5 6 7 8

Table 1: Performances of the utilized MFC using plain and gold-sputtering carbon papers in presence and absence of Yeast Extract (YE)

9 Plain Carbon Paper

Gold-sputtered Carbon paper

YE-free

YE-containing

YE-free

YE-containing

Initial OCV (V)

0.3

0.53

0.45

0.5

Final OCV (V)

0.66

0.76

0.45

0.91

Initial Anode potential (V)

0.45

0.2

0.43

0.25

0.05

-0.15

0.29

-0.15

94

190

25

300

12.9

32.6

2

70

22

13

5

8

Final Anode potential (V) Maximum Current density (mA/m2) Maximum Power density (mW/m2) Stability time (h) 10 11 12 13



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1 2 3 4 5 6 7 8 9 10 11

5 3

6

12 13 14

Fig. 1

15 16 17 18 19 20 21 22


Page 22 of 31

Page 23 of 31

1 2 3 4 5 6

OCV [V], potential [V vs. NHE pH7]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


OCV/ DY

0.6 0.4 0.2

Anode/ DY ocv anode ocv anode

0 -0.2

7 8

OCV/DY+YE

0.8

0

5

Anode/ DY+YE 10

15

20

Time [h] Fig. 2

9 10 11 12 13 14 15 16 17 18


25

30


1 2 3 4 5 6 Electrode potential [V, vs. NHE pH7]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 31

0.8 (a) Cathode

0.6 0.4 0.2

0 -0.2

Anode

0

DY DY+YE 50

100

150 2

7

Current density [mA/m ]

8


200

Page 25 of 31

0.8

40 DY DY+YE

Cell voltage [V]

0.7

(b) 35 30

0.5

25

0.4

20

0.3

15

0.2

10

0.1

5

0

0

50

100

150

0 200

2

1 2

Current density [mA/m ] Fig. 3

3 4 5 6

2


250 DY+YE DY

200 150 100 50 0

7 8

0

1

2 3 Time [h]

4

Fig. 4


5

2

0.6

Power density [mW/m ]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

(a)

21


Page 27 of 31

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(b)

1 2 3

Fig. 5

4 5 6



OCV, potential [V vs. NHE pH 7]

1 OCV/DY+YE

0.8 0.6

OCV/ DY 0.4 Anode/ DY

0.2 0 -0.2

Anode/ DY+YE 0

5

10

2

15

20

Time [h]

1 Fig. 6

3

Electrode potential [V vs. NHE pH 7]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 31

0.8 (a)

Cathode

0.6 0.4 Anode

0.2 0

DY DY+YE

-0.2

0

50

100

150

200

250 2

4

Current density [mA/m ] 28 ACS Paragon Plus Environment

300

25

Page 29 of 31

1

80 (b) DY

Cell voltage [V]

0.8

DY+YE

70 60 50

0.6

40 0.4

30

10 0

0

50

100

150

200

250

300

0 350

2

1 2

Current density [mA/m ] Fig. 7

3 4 5 6

(a)


2

20

0.2

Power density [mW/m ]

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 31

(b)

1

Fig. 8

2


Page 31 of 31

5000 4000 2


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


3000

YE 0.1g/l YE 1 g/l YE 10g/l YE 100g/l

2000 No Glucose 1000 0 -1000 -2000 -0.4

-0.2

0

0.2

0.4

0.8

Electrode potential [ V vs. NHE pH 7]

1 2 3

0.6

Fig. 9.


1

Yeast Extract as an Effective and Safe Mediator for the Baker's-Yeast

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