Researchers at the South Dakota School of Mines & Technology
are studying ways to harness electricity generated by a unique set of microbes.
“We’re studying the electric eels of the microbial
world,” says Navanietha Krishnaraj, Ph.D., a research scientist in the Chemical
and Biological Engineering department at SD Mines.
Researchers, such as Venkata Gadhamshetty,
Ph.D., an associate professor in the Civil and Environmental Engineering
department at SD Mines, and his team including Namita Shrestha, Ph.D., are
working on maximizing the efficiency of what’s known as bioelectrochemical
systems. By understanding the right combination of microbes and materials
it’s possible to harness clean energy for widespread use in various
applications.
Possible outcomes of this research include
new ways to generate electricity and treat
solid waste during NASA space missions, the ability for a wastewater
treatment plants to help generate electricity while turning effluent into clean
water, a new way to clean saline wastewater generated in oil drilling
operations, and better ways to turn food waste, like
tomatoes and corn stover into electricity.
Tapping
the Source with Graphene Armor
Researchers face a challenge in building a system that
efficiently harnesses electricity from that bacteria. Currently a limited
amount of electricity can be drawn from bioelectrochemical systems such as
microbial fuel cells. The bacteria that
generate electricity sometimes have conductive proteins on the surface of their
cell walls and sometimes they can produce mediators that help in transferring
the electricity they generate. But the
microbes don’t react well with the wires, or electrodes, needed to transfer
electricity. The electrodes are not efficient at pulling electricity out of the
electroactive microorganisms.
But a research team at SD Mines in the Composite
and Nanocomposite Advanced Manufacturing – Biomaterials Center (CNAM-Bio)
has found a novel solution. They wrapped
the microorganisms with graphene sheets. Graphene is an ultra-thin form of
graphite (as used, for example, in pencils!) with exceptional electronic
properties. Researchers found that microbes wrapped with graphene showed an enhanced
electron transfer rate for bioelectricity generation. This breakthrough could enable the
development of more efficient bioelectrochemical systems.
“The use of wrapping strategy helps to harness the
maximum number of electrons from the conductive membrane proteins in the surface
of the microbes and transfer them to the electrodes,” says Navanietha
Krishnaraj, an author of this article. “This strategy will help to increase the
electron transfer kinetics leading to improved performance of microbial fuel
cells, microbial electrolysis, microbial desalination cells, microbial
electrosynthesis, and electromethanogenesis.”, adds Rajesh Sani, Ph.D., Associate
Professor in the Chemical and Biological Engineering Department.
The research, presented by Krishnaraj, won first
place in the student poster contest at the Western South Dakota
Hydrology conference in 2018.
The
Potential of Extremophiles
The microbes used in this research were found in the
Sanford Underground Research Facility, formerly known as the Homestake Mine.
Researchers at SD Mines found these microbes while sampling
about 5000 feet below the surface in the former gold mine. Microbes
that live in extreme environments deep underground have evolved unique
properties that make them suitable for these kinds of applications.
This work is supported by National Science Foundation-Building
Genome-to-Phenome Infrastructure for Regulating Methane in Deep and Extreme
Environments (BuG
ReMeDEE) initiative.