new findings

Houston researchers make breakthrough on electricity-generating bacteria

A team of Rice researchers, including Caroline Ajo-Franklin and Biki Bapi Kundu, has uncovered how certain bacteria breathe by generating electricity. Photo by Jeff Fitlow/Rice University.

New research from Rice University that merges biology with electrochemistry has uncovered new findings on how some bacteria generate electricity.

Led by Caroline Ajo-Franklin, a Rice professor of biosciences and the director of the Rice Synthetic Biology Institute, the team published its findings in the journal Cell in April. The report showed how some bacteria use compounds called naphthoquinones, rather than oxygen, to transfer electrons to external surfaces in a process known as extracellular respiration. In other words, the bacteria are exhale electricity as they breathe.

This process has been observed by scientists for years, but the Rice team's deeper understanding of its mechanism is a major breakthrough, with implications for the clean energy and industrial biotechnology sectors, according to the university.

“Our research not only solves a long-standing scientific mystery, but it also points to a new and potentially widespread survival strategy in nature,” Ajo-Franklin, said in a news release.

The Rice team worked with the University of California, San Diego's Palsson lab to simulate bacterial growth using advanced computer modeling. The simulations modeled oxygen-deprived environments that were rich in conductive surfaces, and found that bacteria could sustain themselves without oxygen. Next, they confirmed that the bacteria continued to grow and generate electricity when placed on conductive materials.

The team reports that the findings "lay the groundwork for future technologies that harness the unique capabilities" of these bacteria with "far-reaching practical implications." The team says the findings could lead to significant improvements in wastewater treatment and biomanufacturing. They could also allow for better bioelectronic sensors in oxygen-deprived environments, including deep-sea vents, the human gut and in deep space.

“Our work lays the foundation for harnessing carbon dioxide through renewable electricity, where bacteria function similarly to plants with sunlight in photosynthesis,” Ajo-Franklin added in the release. “It opens the door to building smarter, more sustainable technologies with biology at the core.”

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A View From HETI

Rice University scientists' “recharge-to-recycle” reactor has major implications for the electric vehicle sector. Photo courtesy Jorge Vidal/Rice University.

Engineers at Rice University have developed a cleaner, innovative process to turn end-of-life lithium-ion battery waste into new lithium feedstock.

The findings, recently published in the journal Joule, demonstrate how the team’s new “recharge-to-recycle” reactor recharges the battery’s waste cathode materials to coax out lithium ions into water. The team was then able to form high-purity lithium hydroxide, which was clean enough to feed directly back into battery manufacturing.

The study has major implications for the electric vehicle sector, which significantly contributes to the waste stream from end-of-life battery packs. Additionally, lithium tends to be expensive to mine and refine, and current recycling methods are energy- and chemical-intensive.

“Directly producing high-purity lithium hydroxide shortens the path back into new batteries,” Haotian Wang, associate professor of chemical and biomolecular engineering, co-corresponding author of the study and co-founder of Solidec, said in a news release. “That means fewer processing steps, lower waste and a more resilient supply chain.”

Sibani Lisa Biswal, chair of Rice’s Department of Chemical and Biomolecular Engineering and the William M. McCardell Professor in Chemical Engineering, also served as co-corresponding author on the study.

“We asked a basic question: If charging a battery pulls lithium out of a cathode, why not use that same reaction to recycle?” Biswal added in the release. “By pairing that chemistry with a compact electrochemical reactor, we can separate lithium cleanly and produce the exact salt manufacturers want.”

The new process also showed scalability, according to Rice. The engineers scaled the device to 20 square centimeters, then ran a 1,000-hour stability test and processed 57 grams of industrial black mass supplied by industry partner Houston-based TotalEnergies. The results produced lithium hydroxide that was more than 99 percent pure. It also maintained an average lithium recovery rate of nearly 90 percent over the 1,000-hour test, showing its durability. The process also worked across multiple battery chemistries, including lithium iron phosphate, lithium manganese oxide and nickel-manganese-cobalt variants.

Looking ahead, the team plans to scale the process and consider ways it can sustain high efficiency for greater lithium hydroxide concentrations.

“We’ve made lithium extraction cleaner and simpler,” Biswal added in the release. “Now we see the next bottleneck clearly. Tackle concentration, and you unlock even better sustainability.

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