Biology Reference
In-Depth Information
2 MΩ variable resistors (652-3296Y-1-205LF, Mouser Electronics, Mansfi eld, TX) in
pairs on a circuit board, connected correspondingly to the 24 MFC wells. For environ-
mental screening of microbes using the MFC array, both the primary screening and the
secondary confi rmation started 1,000 min after loading microbes into the MFC array
loaded with 1 MΩ resistors. One, 10, 20, 50, 100, 200, 500, 1,000, and 2,000 KΩ load-
ing resistors were used and voltages across these resistors were continuously recorded.
RESULTS AND DISCUSSION
We recognized that selection of an appropriate anode material would be critical to the
successful development of an MFC array and therefore initiated our studies by exam-
ining the performance of a commonly used anode material, carbon cloth in comparison
to gold in a conventional MFC device (Figure 1). We used the model facultative anaer-
obe
S. oneidensis
MR-1 for these experiments because this organism had previously
proven useful for the development of MFC applications [37]. The MFC power output
was monitored for 5 hr after bacteria were introduced into the device. When the MFC
was loaded with a 20 KΩ resistor, the gold electrode supported maximal power density
of 3.77 ± 0.02 mW/m
2
at a current density of 16.47 ± 0.04 mA/m
2
. A high standard de-
viation was observed (10% deviation). However, the MFC with gold anode displayed
greater reproducibility (3.1% deviation). The open circuit voltage (OCV) of MFCs
containing gold and carbon cloth anodes was 514 ± 12 mV (mean ± SE, n = 3) and 538
± 51 mV (mean ± SE, n = 4), respectively. These results indicated that the OCV of the
MFC with the gold anode was comparable to the corresponding OCV with the carbon
cloth anode. However, OCV measurements with the carbon cloth anode displayed
greater variance.
Figure 1.
Au working as anode of MFC. Power density versus current density from an MFC with gold
anode (n = 3).
