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Supplementary Information
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For
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Mass transfer studies of Geobacter sulfurreducens biofilms on rotating disk
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electrodes
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Jerome T. Babauta, Haluk Beyenal*
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The Gene and Linda Voiland School of Chemical Engineering and Bioengineering, Washington
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State University, Pullman, WA, USA
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Short running title: Geobacter sulfurreducens and electron transfer
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* Corresponding author.
Email: beyenal@wsu.edu
Phone: 509-334-0896
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Q1
Q1
R1
R2 +R3
R1
R2 +R3
C1*
R2(R2 +R3)/R3 R32Q2/(R2 +R3)2
R2(R2 +R3)/R3 R32Q2/(R2 +R3)2
A
B
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Figure SI-1. Equivalent electrical circuit models (A,B) that are identical to Figure1A and Figure
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1B but linearly transformed, respectively.
Zmod ( )
100000
No biofilm
i+300 = 2.3 A
10000
i+300 = 5.0 A
i+300 = 25 A
i+300 = 41 A
i+300 = 82 A
1000
100
1
10
100
1000
10000 100000
Frequency (Hz)
0
Phase angle (°)
-10
-20
-30
-40
No biofilm
i+300 = 2.3 A
-50
i+300 = 5.0 A
i+300 = 25 A
-60
i+300 = 41 A
i+300 = 82 A
-70
1
26
10
100
1000
Frequency (Hz)
2
10000 100000
-375 mVAg/AgCl. EAC was 5 mV. Frequency range was 100000 Hz – 0.1 Hz.
800
Complex plane plot
700
f = 0.50 Hz
500
f = 0.32 Hz
400
200
100
500
1000
1500
2000
Zreal ( )
2500
5
0
Zreal
-5
-5
-Zimage
-10
-10
1
10
100
1000
10000
100000
60
60
EEC (Figure 1A) Residuals
Goodness of fit = 30.97e-6
40
20
40
20
0
0
Zreal
-20
-20
-Zimage
1
10
100
1000
10000
100000
-10
1500
-20
1000
-30
500
Phase angle (°)
0
2000
Zmod ( )
0
10
Frequency (Hz)
Bode plot
i+300 = 82 mA (Zmod)
Data points not included in fit
due to noise
Kramers Kronig fit (Zmod)
Fit using EEC (Zmod; Figure 1A)
i+300 = 82 mA (phase angle)
Kramers Kronig fit (phase angle)
Fit using EEC (phase angle; Figure 1A)
-40
0
1
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Kramers Kronig Residuals
Goodness of fit = 12.52e-6
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Frequency (Hz)
i+300 = 82 A
Data points not included in fit
due to noise
Fit using EEC (Figure 1A)
Kramers Kronig fit
300
Residuals from Zreal (m )
-Zimag ( )
600
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Residuals from -Zimage (m )
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Residuals from -Zimage (m )
Figure SI-2. Corresponding Bode plot to the complex plane plot shown in Figure 4B. EDC was
Residuals from Zreal (m )
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10
100
1000
-50
10000 100000
Frequency (Hz)
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Figure SI-3. Example of the EEC (Figure 1A) fit to the impedance data at a current of 82 μA. A
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fit using Kramers Kronig transformations is also shown. Residuals for each respective fit and the
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goodness of fit are also shown. EDC was -340 mVAg/AgCl. EAC was 5 mV. Frequency range was
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100000 Hz to 0.1 Hz.
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3
120
Started feeding acetate-free
growth media (1 L total)
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4
3
2
60
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8.3
8.5
8.6
8.8
8.9
9.0
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Performed second
rotation test at only ~3 A
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0
100
0
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Current ( A)
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Current ( A)
Current ( A)
100
5
-2
60
40
20
0
Started rotation tests
to see effect of acetate
limitation
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-0.6
-0.4
-0.2
0.0
Potential (VAg/AgCl)
0.2
-4
0.0
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1.4
2.8
4.2
5.6
6.9
8.3
-0.6
Time (hours)
-0.4
-0.2
0.0
0.2
Potential (VAg/AgCl)
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Figure SI-4. Current decrease during acetate removal by washout with acetate-free growth media
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(left). Non-turnover slow-scan cyclic voltammogram of the G. sulfurreducens biofilm (right).
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Scan rate was 1 mV/sec. The inset shows the transition from turnover to non-turnover conditions
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using cyclic voltammetry at a scan rate of 10 mV/sec. From top to bottom, each represents the
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condition where normalized current was 100%, 30%, 2%, <1%.
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-Zimag ( )
10000
<1%, 530 RPM
Fit using EEC (Figure 1B)
Kramers Kronig fit
8000
6000
f = 0.04 Hz
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Kramers Kronig Residuals
Goodness of fit = 20.32e-6
10
5
0
0
Zreal
-5
-Zimage
-10
0.01
Residuals from Z real (m )
2000
f = 0.032 Hz
1000
2000
3000
4000
5000
Zreal ( )
0.1
1
100
1000
10000
-10
100000
150
EEC (Figure 1B) Residuals
Goodness of fit = 107.0e-6
100
50
0
0
-50
-100
-150
0.01
10000
-10
8000
-20
6000
-30
4000
-40
2000
-50
0
-60
10
100
Phase angle (°)
0
1
-50
Zreal
-100
-Zimage
0.1
1
10
100
1000
10000
-150
100000
Frequency (Hz)
12000
0.1
100
50
Bode plot
Zmod ( )
10
150
14000
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-5
Frequency (Hz)
4000
0.01
10
5
<1%, 530 RPM (Zmod)
Kramers Kronig fit (Zmod)
Fit using EEC (Zmod; Figure 1B)
<1%, 530 RPM (phase angle)
Kramers Kronig fit (phase angle)
Fit using EEC (phase angle; Figure 1B)
-70
1000 10000 100000
Frequency (Hz)
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Figure SI-5. Example of the EEC (Figure 1B) fit to the impedance data taken at 530 RPM in
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Figure 6D. A fit using Kramers Kronig transformations is also shown. Residuals for each
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respective fit and the goodness of fit are also shown. EDC was -340 mVAg/AgCl. EAC was 5 mV.
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Frequency range was 100000 Hz to 0.01 Hz.
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Residuals from -Zimage (m )
Complex plane plot
Residuals from -Zimage (m )
Residuals from Z real (m )
12000
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Table SI-1. Fitted parameters using the EEC in Figure 1B corresponding to the impedance data shown in Figure 6A and Figure 6D.
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These are the original values obtained from the fit. Reported values in the main text round the original values to the first two
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significant digits.
100%, 0 RPM
R1
Ω
155.1±1.26
R2
Ω
512±317
R3
Ω
1070±348
Q1×10-5
sα/Ω
3.96±1.51
100%, 530 RPM
154.4±1.26
552±341
901±363
<1%, 0 RPM
154.5±1.26
810±221
<1%, 530 RPM
150.9±1.22
900±181
Condition
0.86±0.05
Q2×10-5
sα/Ω
14.7±4.24
0.63±0.08
C1×10-5
F
--
4.11±1.53
0.86±0.05
13.0±4.53
0.67±0.09
--
9.65e-5
4152±279
5.43±1.05
0.82±0.03
20.2±1.36
0.61±0.03
74.2±4.10
238.5e-6
4237±255
4.88±0.778
0.83±0.02
21.4±1.39
0.62±0.03
75.7±4.27
107.0e-6
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α1
α2
Goodness of fit
1.06e-4
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Heme content (nmol)
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105
104
103
102
101
100
10-1
-0.40 -0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00
E (V)
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Figure SI-6. A plot showing the dependence of heme content on ΔE. Heme content calculated based off of Eq (1) and a
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pseudocapacitance, C1, of 740 μF. ΔE for the biofilm is indicated by the vertical solid line and is the difference between the biofilm
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open circuit potential, -460 mVAg/AgCl, and the formal potential of the overall electron transfer mechanism, -340 mVAg/AgCl.
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