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Matti Leisola on why lignin (wood) remains engimatic, in terms of evolution


Our lignin paper has caused some discussion around the claim “that no living organism is able to use it [lignin] as a sole carbon and energy source, despite the fact that it is the most abundant energy-rich aromatic polymer on earth.” There are reports that seem to indicate that some bacteria can degrade and use lignin as a carbon source [most recently Chen YH et al. (2012) Biodegradation of kraft lignin by a bacterial strain Comamonas sp. B-9 isolated from eroded bamboo slips. J Appl Microb 112: 900-906].

We do say in our paper that “some bacteria can use monolignols as an energy and carbon source, and there are reports that some bacteria degrade plant cell walls by mechanisms called tunneling, erosion and cavitation. However, since lignin almost always contains sugars, it is likely that these processes depend on energy derived from the sugars. Using 14C-labelled lignins it has been possible to show that bacteria from some genera, like Streptomyces, Nocardia and Rhodococcus, do degrade lignin, which is consistent with the identification of a bacterial lignin peroxidase. Degradation is slow and proceeds to a limited extent, with most of the metabolized 14C being in the side chains. Typically several weeks are needed to achieve roughly 10% degradation of lignins below 1,000 daltons in molecular weight, and oxygen is always needed. “

How are we to interpret the results obtained by Chen et al.? They used kraft lignin, which is produced in an alkaline cooking process (several hours at 130 to 180̊C).

(July 27, 2012) More.


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