Biology Reference
In-Depth Information
microscopic drug-delivery systems [17] and renewable energy systems [18]. In
addition, MFCs hold signifi cant promise for supporting civilian and combat opera-
tions in hostile environments [16]. Therefore, the development of effi cient MFCs that
are capable of producing high power densities remains an area of intense research
interest. However, economical applications of existing MFCs are limited due to their
low power output [19], which ranges from 100 to 1,000 W/m
3
[20, 21].
Important strategies for enhancing MFC performance include engineering opti-
mized microbes (and microbial communities) for use in these devices [22] and im-
proving cultivation practices for these organisms [23, 24]. To date, detailed description
of individual microbe performance in MFCs has been limited to a surprisingly small
number of organisms [25]. The MFCs that are fed by sediment and wastewater nutrient
sources and that exploit mixed microbial consortia for electricity generation have been
described [26, 27]. However, with the conventional two-bottle MFCs, characterization
of the electrochemical activities of the microbial species in these consortia has not
been possible because these conventional MFCs are not suitable for parallel analyses
due to their bulkiness. To address this issue, MFC systems that support parallel, low
cost, and reproducible analysis of the electrochemical activities of diverse microbes
are required. High throughput microarrays, including DNA microarrays, protein mi-
croarrays, and cell arrays, are powerful platforms for screening and analyzing diverse
biological phenomena [28]. Various MFC platforms, including miniature MFC de-
vices that enable parallel comparison of electricity generation in MFCs, are emerging
[29, 30]. However, state of the art microfabrication and highly integrated parallel mea-
surement approaches [31, 32] have not yet been exploited to construct an MFC array
with highly consistent architecture and performance.
Here we describe our development of a compact and user-friendly MFC array
prototype capable of examining and comparing the electricity generation ability of
environmental microbes in parallel. The parallel analyses platform can greatly speed
up research on electricigens. Importantly, the array was fabricated using advanced
microfabrication approaches that can accommodate scale-up to massively parallel sys-
tems. The MFC array consisted of 24 integrated cathode and anode pairs as well as 24
cathode and anode chambers, which functioned as 24 independent miniature MFCs.
We validated the utility of our MFC array by screening environmental microbes for
isolates with enhanced electrochemical activities. Our highly compact MFC array en-
abled parallel analyses of power generation of various microbes with 380 times less
reagents, and was 24-fold more effi cient than conventional MFC confi gurations. This
effort identifi ed a
Shewanella
isolate that generates more than twice as much power
as the reference strain when tested in both conventional and microfabricated array
formats.
MATERIALS AND METHODS
Twenty-four Well MFC Array Design
Figure 2A shows the schematic illustration of the MFC array. The array was micro-
fabricated using micromachining and soft lithography techniques. The 24-well de-
vice was composed of layered functional compartments in which microbe culture
