Researchers at the South Dakota School of Mines & Technology are studying ways to harness electricity generated by a unique set of microbes, with compelling applications for wastewater.

“We’re studying the electric eels of the microbial world,” said 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 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.

Researchers are challenged 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 wires or electrodes needed to transfer electricity. The electrodes are not efficient at pulling electricity out of the electroactive microorganisms.

Addressing this, research conducted at the Composite and Nanocomposite Advanced Manufacturing – Biomaterials Center (CNAM-Bio) has found a solution, wrapping the microorganisms with graphene sheets. 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,” said Krishnaraj.

“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,” said Rajesh Sani, Ph.D., associate professor in the Chemical and Biological Engineering Department.

These findings are described in the article, Rewiring the Microbe-Electrode Interfaces with Biologically Reduced Graphene Oxide for Improved Bioelectrocatalysis, published in the journal Bioresource Technology. This work was conducted by Navanietha Krishnaraj Rathinam, Rajesh K. Sani, and David R. Salem from South Dakota School of Mines and Technology, and Sheela Berchmans from the Central Electrochemical Research Institute.


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