THESIS
2015
iii leaves, iv-xiv, 68 pages : illustrations (some color) ; 30 cm
Abstract
Solar powered microbial fuel cell (photo-MFC) is a potential candidate for harnessing solar
energy as a clean and environmental-friendly energy source. In a conventional MFC, the
generation of bioelectricity can be achieved by using microorganisms in the anode as cheap
and regenerative biocatalyst. By applying phototrophic inoculum, solar energy can be
incorporated into central metabolism of anode microbes and contribute directly or indirectly
to the bioelectricity generation. In the past decades, cyanobacteria arose most attention in the
photo-MFC development owing to their remarkable light harvesting capability and self-sustainability
by fixing atmospheric CO
2 into carbohydrate. However, it generates oxygen as
a byproduct during photosynthesis, which scavenges electrons and se...[
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Solar powered microbial fuel cell (photo-MFC) is a potential candidate for harnessing solar
energy as a clean and environmental-friendly energy source. In a conventional MFC, the
generation of bioelectricity can be achieved by using microorganisms in the anode as cheap
and regenerative biocatalyst. By applying phototrophic inoculum, solar energy can be
incorporated into central metabolism of anode microbes and contribute directly or indirectly
to the bioelectricity generation. In the past decades, cyanobacteria arose most attention in the
photo-MFC development owing to their remarkable light harvesting capability and self-sustainability
by fixing atmospheric CO
2 into carbohydrate. However, it generates oxygen as
a byproduct during photosynthesis, which scavenges electrons and severely reduces the
current collected via external circuit.
Rhodobacter sphaeroides, a purple non-sulfur bacterium that performs highly efficient
anoxygenic photosynthesis, could serve as a potential substitute for cyanobacteria in photo-MFC. The well-established culturing methods and genetic manipulation tools have paved
ways for the study of R. sphaeroides as a model organism in bacterial photosynthesis.
Moreover, this metabolic versatile species can grow by respiring a wide range of organic substrate, which holds a great promise in sustaining the electricity generation process in
complex medium such as wastewater.
In this study, a steady current generation of wild type R. sphaeroides was observed during
chronoamperometric measurement without involving the in-situ oxidation of hydrogen. Using
glassy carbon as the anode and Sistrom’s minimal medium as the electrolyte in a three
electrode system, the bioelectricity generation synchronized with the supplementation of
reduced carbon source and showed instantaneous response to illumination. The result
indicated that the genetic manipulation of endogenous electron transfer pathways in R.
sphaeroides has significantly affected the bioelectricity output, which strongly argues a
correlation between observed current and cytoplasmic Quinone pool (Q) -mediated electron
chains. This study represents a pioneering work in utilizing genetic engineering tools for
improving efficiency of a photo-MFC, which motivates further investigations into anode
strain optimization. It is also anticipated that the observed correlation between current output
and electron chain manipulation would be of great interests for study of bioenergetics in
photosynthetic bacteria.
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