A study by the Department of Energy's Joint BioEnergy Institute (JBEI) and the Lawrence Berkeley National Laboratory shows certain anaerobic fungi called Neocallimastigomycetes could provide a breakthrough in biofuel technology.
The study, which was published in the journal Nature Microbiology, found that Neocallimastigomycetes can break down plant cell walls and lignin, according to a Berkeley Lab report. The focus of the institute's mission is to discover novel microbes and enzymes that can perform this task.
“You can think of lignin as kind of a skeletal system for plants,” said Michelle O'Malley, a professor of chemical and biological engineering at the University of California Santa Barbara and deputy director for microbial and enzyme discovery at the Energy Department’s Joint BioEnergy Institute. “Lignin is really important – it provides that hardiness and structure, but it’s equally difficult to break down for the exact same reason.”
Previously, scientists thought that lignin could only be broken down in the presence of oxygen.
“It takes time and depends on certain chemical species – such as free oxygen radicals – that to the best of everyone’s knowledge could only be made with the help of oxygen,” O’Malley said. “We’ve never had to extract the lignin out of there because the fungi we work with are just happy to extract the cellulose and hemicellulose on their own.”
The potential for these fungi to grow on non-pretreated plant biomass is unique and unusual, O’Malley added.
“We hypothesized that they must have a way of moving the lignin around,” she said.
Researchers used nuclear magnetic resonance spectroscopy to identify specific lignin bond breakages in the absence of oxygen and break down cell walls, according to the report.
“The nuclear magnetic resonance showed that sorghum biomass is favored by the anaerobic fungi, as compared to switchgrass and poplar,” said Yu Gao, a co-author of the study and a project scientist in the plant systems biology group at JBEI. “We were excited to see almost complete breakdown of the key structural bonds between lignin monomers in the sorghum.”
O'Malley said this breakthrough will only lead to more experiments and further collaboration.
“This is really a paradigm shift in terms of how people think about the fate of lignin in the absence of oxygen,” O'Malley said. “You could extend this to understand what happens to lignin in a compost pile, in an anaerobic digester, or in very deep environments where no oxygen is available. It pushes our understanding of what happens to biomass in these environments and alters our perception of what’s possible and the chemistry of what’s happening there.”
