A team of researchers from the U.S. National Science Foundation (NSF) Center for Sustainable Polymers, based at the University of Minnesota-Twin Cities (Minneapolis, Minnesota), have developed a chemical technology of combined fermentation and chemical refining that can produce petroleum-like liquids from renewable plants. These renewable liquids have potential applications as a more sustainable replacement for fossil fuels used to manufacture plastic containers and bags, automobile parts, lubricants, soaps, and other everyday items.
The study conducted by scientists at the University of Minnesota and the University of California Berkeley (Berkeley, California, USA) was recently published in the journal Nature Chemistry.
In order to make sustainable liquids similar to those found in petroleum, NSF researchers combined two normally independent technologies. First, they obtained glucose found in plants and fermented it with microbes to remove most of the oxygen. Second, metal oxide catalysts stripped the remaining oxygen and combined molecules together to make a useful distribution of olefins, which are considered the building blocks of the chemical industry.
“Our insight early on was that we needed to find a molecule that could be readily made with fermentation that could strip most oxygen from glucose,” says Michelle Chang, a professor of chemistry and chemical and biomolecular engineering at the University of California Berkeley and leader of the project. “We optimized the chemistry to take advantage of the unique capabilities of molecular biology, after which we could solve the rest of the problem with metal nanoparticle catalysts.”
Chang’s group developed a unique strain of Escherichia coli that converted glucose to eight- and 10-carbon hydroxy-acids, which are molecules with only a few oxygen atoms at the end of the chain. The microbes were optimized through genetic engineering so that the group could “grow” these molecules from sugar. According to Chang, the target molecule was designed to have oxygen left in strategic positions to make the downstream conversion more efficient for a group of researchers led by University of Minnesota chemical engineering and materials science professor Paul Dauenhauer.
“The biorenewable molecules that Professor Chang’s group made were perfect raw materials for catalytic refining,” says Dauenhauer, who was one of the co-authors of the research study. “These molecules contained just enough oxygen that we could readily convert them to larger more useful molecules using metal nanoparticle catalysts. This allowed us to tune the distribution of molecular products as needed, just like conventional petroleum products except this time we were using renewable resources.”
Dauenhauer’s lab screened a broad array of catalysts to demonstrate that the bio-petroleum molecules made by fermentation could be converted to a range of important chemicals. The outcomes included small molecules for making key polymers used in plastic bags, mid-size molecules for making rubbery materials, and—even more important—the ability to combined fermentation product molecules to produce larger molecules that help form soap-like molecules and longer chain molecules for lubricants.
Depending on the selected catalyst and reaction conditions, the combined fermentation-catalysis technology could be used to manufacture almost the full slate of unprocessed chemical materials used in manufacturing processes. This hybrid approach also has the benefit of competing economically with conventional products derived from fossil fuels while also improving sustainability.
“This is a unique scientific approach to a new sustainable technology that was facilitated by the synergistic research that happens between disparate research groups supported in the NSF Center for Sustainable Polymers,” says Marc Hillmyer, center director and a University of Minnesota chemistry professor. “The teamwork and combined focus on solving the problem produced a new approach that would not have been possible in either of the individual research groups.”
“This advance from the NSF Center for Sustainable Polymers demonstrates a truly innovative, green entry into the building blocks for valuable polymers/plastics,” says NSF chemistry division director David Berkowitz. “By cleverly combining biology and chemistry, the Chang team has opened a new, potential bio-renewable alternative to petroleum cracking. These results showcase how NSF investments in collaborative, interdisciplinary science can push the envelope toward developing more sustainable chemical industries.”
Source: University of Minnesota College of Science and Engineering, https://cse.umn.edu.