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Rainforest microbe dissolves lignin, shows promise in biofuel production

Rainforest microbe dissolves lignin, shows promise in biofuel production
An expedition into the Luquillo Experimental Forest in Puerto Rico by JBEI and Berkeley Lab researchers led to the identification of a soil microbe that utilizes lignin as its sole source of carbon. Photo from Berkeley Lab

It’s often speculated that many a cure for society’s ills – cancer, AIDS, the need for new fuel sources - could be found in an yet unknown living organism that is living in the world’s rich but fast disappearing rainforests.

Now, scientists from the U.S.-based Joint BioEnergy Institute at the Lawrence Berkeley National Laboratory have found a microbe living in the soil of the rainforest that can dissolve lignin, that tough woody polymer in plant cell walls that proves to be such an obstacle in cellulosic biofuel production.

It’s been known for a while that certain anaerobic microbes that live in tropical rainforests utilize lignin as their sole source of carbon.

“Tropical soil microbes are responsible for the nearly complete decomposition of leaf plant litter in as little as eighteen months,” said Kristen DeAngelis, a microbial ecologist formerly of JBEI and now with the University of Massachusetts.

“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,” she said.

Ms. DeAngelis led an expedition to the Luquillo Experimental Forest in Puerto Rico where they harvested soil microbes.

According to Blake Simmons, a chemical engineer with JBEI, they were able to observe that one of these soil microbes known as Enterobacter lignolyticus SCF1 can degrade lignin over time by absorbance. They believe that the enzymes used by E. lignolyticus to degrade lignin could be used to improve biofuel production.

Ms. DeAngelis, Mr. Simmons and their colleagues were able to characterize the mechanisms by with E. lignolyticus degraded 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,” Mr. Simmons said.

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

The next step in the research would be to determine what kind of chemical bonds are preferred by these two ways of degrading lignin. This would help researchers to better develop ways to use the bacteria and its enzymes in the biofuel process. – EcoSeed Staff

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