A new feat in biofuel production outsourced via Fungi

April 15, 2023 | Microbiology Lab

A study proves that tough, woody lignin can be broken down by fungi in an anaerobic environment. Such findings are a key milestone in plant-based biofuel production in the future.

Lignin is a structural and organic polymer that gives woody plants and trees strength and rigidity. Lignin is one of the most abundant terrestrial polymers and it surrounds many valuable plant fibers and molecules that may be converted into biofuels and other commodity chemicals–if only lignin will break down and we get past it.

Fortunately, UC Santa Barbara chemical engineering and biological engineering professor Michelle O’Malley and her team found and prove that a fungus, Neocallimastigomycetes, is actually capable of breaking down lignin.

O’Malley, Deputy Director for Microbial and Enzyme Discovery at the Department of Energy (DOE)’s Joint BioEnergy Institute (JBEI) along with her team has been keen on locating targeted ecosystems and discovering novel microbes and enzymes in them, which could break down plant cell walls, including lignin.

Since lignin has properties that make plants resistant to physical degradation by enzymes and pathogens, it was thought for decades that lignin could only be degraded by free oxygen radicals which takes a lot of time.

But upon discovery of the potential of Neocallimastigomycetes based on genetic findings, O’Malley conducted an experiment on the fungi by cultivating them on poplar, sorghum, and switchgrass biomass in an oxygen-free environment.

And true to their assumptions, it was found that Neocallimastix californiae is indeed capable of breaking down the plants’ tough cell walls. Using nuclear magnetic resonance spectroscopy performed at JBEI, researchers are able to identify specific lignin bond breakages in the absence of oxygen.

“The nuclear magnetic resonance showed that sorghum biomass is favored by the anaerobic fungi, as compared to switchgrass and poplar,” says Yu Gao, co-author, and project scientist in the Plant Systems Biology group at JBEI. “We were excited to see an almost complete breakdown of the key structural bonds between lignin monomers in the sorghum.”

The team’s next challenge is focused on discovering the mechanism by which the fungi are able to break down lignin in oxygen-free environments. They are keen on checking possible enzymes mediating the process, or which features of the anaerobes catalyze the breakdown of lignin.

Currently, researchers are looking forward to future work detailing the fungi’s lignin-digesting machinery. They are also interested in delving into the other functions that such microbes can offer.

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