Lignin-feasting microbe holds promise for biofuels

November 13, 2013

Nature designed lignin, the tough woody polymer in the walls of plant cells, to bind and protect the cellulose sugars that plants use for energy. For this reason, lignin is a major challenge for those who would extract those same plant sugars and use them to make advanced biofuels. As part of their search for economic ways to overcome the lignin challenge, researchers at the Joint BioEnergy Institute (JBEI) have characterized the enzymatic activity of a rain forest microbe that breaks down lignin essentially by breathing it.

"Using a combination of transcriptomics and proteomics we observed the anaerobe Enterobacter lignolyticus SCF1 as it grows on lignin," says Blake Simmons, a chemical engineer who heads JBEI's Deconstruction Division. "We detected significant lignin degradation over time by absorbance, suggesting that enzymes in E. lignolyticus could be used to deconstruct lignin and improve biofuels production. Our results also demonstrate the value of a multi-omics approach for providing insight into the natural processes of bacterial lignin decomposition."

Not only does lignin inhibit access to cellulose, the by-products of lignin degradation can also be toxic to microbes employed to ferment sugars into fuels. This makes finding microbes that can tolerate a lignin environment a priority for biofuels research. Tropical rainforests harbor anaerobic microbes that actually utilize lignin as their sole source of carbon. Kristen DeAngelis, a microbial ecologist formerly of JBEI and now with the University of Massachusetts, has led expeditions to the Luquillo Experimental Forest where she and her crew harvested soil microbes.

"Tropical soil microbes are responsible for the nearly complete decomposition of leaf plant litter in as little as eighteen months," she says. "The fast growth, high efficiency and specificity of enzymes employed in the anaerobic litter deconstruction carried out by these tropical soil bacteria make them useful templates for improving biofuel production."

In an earlier study at JBEI led by DeAngelis, E. lignolyticus SCF1 is a member, was shown to be capable of anaerobic lignin degradation, but the enzymes behind this degradation were unknown. Through their multi-omics approach plus measurements of enzyme activities, DeAngelis, Simmons and their colleagues were able to characterize the mechanisms by which E. lignolyticus SCF1 is able to degrade lignin during anaerobic growth conditions.

"We found that E. lignolyticus SCF1 is capable of degrading 56-percent of the lignin under anaerobic conditions within 48 hours, with increased cell abundance in lignin-amended compared to unamended growth," Simmons says. "Proteomics analysis enabled us to identify 229 proteins that were significantly differentially abundant between the lignin-amended and unamended growth conditions. Of these, 127 proteins were at least two-fold up-regulated in the presence of lignin."

This new study also showed that E. lignolyticus SCF1 is able to degrade lignin via both assimilatory and dissimilatory pathways, the first soil bacterium to demonstrate this dual capability.

"Our next step is to look at what kind of chemical bonds are preferred by these two different pathways of reduction," DeAngelis says. "We can then try to develop tailored routes to targeted intermediates by defining the molecular mechanisms of enzymatic reactions with lignin."
-end-
This work was supported by the University of Massachusetts, Amherst, the Environmental Molecular Sciences Laboratory (EMSL) and JBEI through the U.S. Department of Energy's Office of Science. A paper describing this research has been published in the journal Frontiers in Microbiology (Microbial Physiology and Metabolism) under the title "Evidence supporting dissimilatory and assimilatory lignin degradation in Enterobacter lignolyticus SCF1." In addition to DeAngelis and Simmons, other authors were Deepak Sharma, Rebecca Varney, Nancy Isern, Lye Markillie, Carrie Nicora, Angela Norbeck, Ronald Taylor, Joshua Aldrich and Errol Robinson.

DOE/Lawrence Berkeley National Laboratory

Related Enzymes Articles from Brightsurf:

Bacilli and their enzymes show prospects for several applications
This publication is devoted to the des­cription of different microbial enzymes with prospects for practical application.

Ancient enzymes can contribute to greener chemistry
A research team at Uppsala University has resurrected several billion-year-old enzymes and reprogrammed them to catalyse completely different chemical reactions than their modern versions can manage.

Advances in the production of minor ginsenosides using microorganisms and their enzymes
Advances in the Production of Minor Ginsenosides Using Microorganisms and Their Enzymes - BIO Integration https://bio-integration.org/wp-content/uploads/2020/05/bioi20200007.pdf Announcing a new article publication for BIO Integration journal.

Cold-adapted enzymes can transform at room temperature
Enzymes from cold-loving organisms that live at low temperatures, close to the freezing point of water, display highly distinctive properties.

How enzymes build sugar trees
Researchers have used cryo-electron microscopy to elucidate for the first time the structure and function of a very small enzyme embedded in cell membranes.

Energized by enzymes -- nature's catalysts
Scientists at Pacific Northwest National Laboratory are using a custom virtual reality app to design an artificial enzyme that converts carbon dioxide to formate, a kind of fuel.

Mathematical model reveals behavior of cellular enzymes
Mathematical modeling helps researchers to understand how enzymes in the body work to ensure normal functioning.

While promoting diseases like cancer, these enzymes also cannibalize each other
In diseases like cancer, atherosclerosis, and sickle cell anemia, cathepsins promote their propagation.

Researchers finally grasp the work week of enzymes
Scientists have found a novel way of monitoring individual enzymes as they chomp through fat.

How oxygen destroys the core of important enzymes
Certain enzymes, such as hydrogen-producing hydrogenases, are unstable in the presence of oxygen.

Read More: Enzymes News and Enzymes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.