Fungal End to Coal and the Carboniferous Period: A Possible Solution for Biofuels?
Much of the world’s coal was generated 300-360 million years ago during the Carboniferous period. Wood (a major pool of organic carbon that is highly resistant to decay largely due to its lignin content) was deposited, transformed to peat, and eventually transformed to coal. But coal formation may also have declined from an unlikely source: fungi. These fungi had enzymes (ligninases) capable of degrading lignin, a category of enzyme important for the Department of Energy’s bioenergy mission, since lignin in plant biomass hinders biomass conversion to biofuels. An international team of scientists from Clark University and DOE’s Joint Genome Institute has proposed that a species of fungus, first appearing at about the end of the Carboniferous period, could more efficiently break down dead plant matter, possibly leading to the decline in coal formation. By comparing the genomic sequences of 31 fungi, including 12 sequenced for this study, the researchers showed that genes able to degrade lignin first appeared at the end of this period. Instead of becoming coal, the plant biomass decayed and the carbon was released into the atmosphere as carbon dioxide. This research provides insights into the origin of ligninases that can be used to develop processes for converting plant and tree biomass into bioenergy products.
Floudas, D., et.al. 2012. “The Paleozoic Origin of Enzymatic Lignin Decomposition Reconstructed from 31 Fungal Genomes,” Science 336, 1715-19. DOI: 10.1126/science.1221748.