as pacemakers or mechanical valves. However, in order for such applications to
be realized, EBCs have to be greatly improved in terms of both power output
and long-term performance. Therefore, it will most likely take additional decades
of research before EBCs are able to compete with battery-based solutions for
these kinds of applications. Despite currently lagging behind in this area, the future
of EBCs still looks very bright, and it is likely that these devices will revolutionize
the health care in the near future and become a daily part of our lives.
4 Harnessing Microbes for Nanoparticle Synthesis
As is evident from the many examples presented in this chapter so far, a wide range
of synthetic protocols for preparing nanostructured catalysts with tailored properties
are available. Most often, these protocols rely on the work by chemists, who use
specific combinations of chemical reagents and different synthetic techniques for
the rational design of nanomaterials. However, lately it has been found that bacteria
can aid the production of nanometal species [4, 7]. Apart from offering a green
alternative for generating metal NPs that is free of toxic chemical reagents, this
approach also provides direct access to biometallic whole cell systems (BWCSs) in
which the bacteria also act as supports for the formed metal NPs. As will be shown
in this part, such BWCSs are far from being merely academic curiosities. In fact,
such “living” catalytic systems are very interesting for a number of applications
related to, for example, environmental remediation, energy research, and organic
chemistry [4, 7].
4.1 Biosynthesized Transition Metal Nanoparticles
and Biometallic Whole Cell Systems in Catalysis
The interest for biosynthesized transition metal NPs within the chemistry
community was sparked in 1998, when the group of Macaskie demonstrated
that the sulfate-reducing bacterium Desulfovibrio desulfuricans could be used
for the preparation of Pd NPs. This bacterium was found to produce Pd NPs in
sizes of approximately 50 nm, when it was subjected to an aqueous solution
containing Pd(NH 3 ) 4 Cl 2 and different electron donors (H 2 , formate, and pyruvate)
[117]. After this seminal study, many researchers became interested in searching
for other microorganisms that could be harnessed for the biosynthesis of metal NPs
that are commonly used as catalysts in organic transformations. Soon, it was
found that several other bacteria were also capable of mediating the bioreduction
of metal salts, as, for example, Aeromonas hydrophila [118, 119], Cupriavidus
necator [120], Geobacter sulfurreducens [121, 122], Pseudomonas putida [120],
Pseudomonas stutzeri [123], and Shewanella oneidensis [124, 125]. Of these,
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be realized, EBCs have to be greatly improved in terms of both power output
and long-term performance. Therefore, it will most likely take additional decades
of research before EBCs are able to compete with battery-based solutions for
these kinds of applications. Despite currently lagging behind in this area, the future
of EBCs still looks very bright, and it is likely that these devices will revolutionize
the health care in the near future and become a daily part of our lives.
4 Harnessing Microbes for Nanoparticle Synthesis
As is evident from the many examples presented in this chapter so far, a wide range
of synthetic protocols for preparing nanostructured catalysts with tailored properties
are available. Most often, these protocols rely on the work by chemists, who use
specific combinations of chemical reagents and different synthetic techniques for
the rational design of nanomaterials. However, lately it has been found that bacteria
can aid the production of nanometal species [4, 7]. Apart from offering a green
alternative for generating metal NPs that is free of toxic chemical reagents, this
approach also provides direct access to biometallic whole cell systems (BWCSs) in
which the bacteria also act as supports for the formed metal NPs. As will be shown
in this part, such BWCSs are far from being merely academic curiosities. In fact,
such “living” catalytic systems are very interesting for a number of applications
related to, for example, environmental remediation, energy research, and organic
chemistry [4, 7].
4.1 Biosynthesized Transition Metal Nanoparticles
and Biometallic Whole Cell Systems in Catalysis
The interest for biosynthesized transition metal NPs within the chemistry
community was sparked in 1998, when the group of Macaskie demonstrated
that the sulfate-reducing bacterium Desulfovibrio desulfuricans could be used
for the preparation of Pd NPs. This bacterium was found to produce Pd NPs in
sizes of approximately 50 nm, when it was subjected to an aqueous solution
containing Pd(NH 3 ) 4 Cl 2 and different electron donors (H 2 , formate, and pyruvate)
[117]. After this seminal study, many researchers became interested in searching
for other microorganisms that could be harnessed for the biosynthesis of metal NPs
that are commonly used as catalysts in organic transformations. Soon, it was
found that several other bacteria were also capable of mediating the bioreduction
of metal salts, as, for example, Aeromonas hydrophila [118, 119], Cupriavidus
necator [120], Geobacter sulfurreducens [121, 122], Pseudomonas putida [120],
Pseudomonas stutzeri [123], and Shewanella oneidensis [124, 125]. Of these,
262
O. Verho and J.-E. Bäckvall