It is a biodegradable substance that is likely to be cheaper to produce with the help of microorganisms than synthesizing analogs from petroleum. The raw material is obtained from wood as waste paper production.
In addition to cellulose, lignin is present in the tissues of trees, shrubs and grasses. It is a three-dimensional polymer composed mainly of a large number of phenylpropane (C9H10) molecules. In modern plants, it provides mechanical strength by holding cellulose fibers together and also seals the body and its cells.
The lignin content ranges from 38% in some conifers to 20% in cereals. It is obtained during the production of paper and up to 98% of it is immediately burned. The rest is processed into fuel briquettes, or even buried in the ground. People have not come up with any more useful use for it, but there is no harm from lignin either. The substance is not poisonous, but living next to its graves is still not worth it - it burns very well.
The difficulty in getting something useful out of lignin is the size of its molecule. It is very large and, in order to obtain aromatic hydrocarbons from it, similar to those of which there are so many in oil, it must be split into “bricks”. Modern chemistry, of course, can do it, but it is difficult and expensive. It is much cheaper to take finished raw materials from oil.
A group of scientists from the American University of Wisconsin-Madison tried to solve this problem. They used the bacteria Novosphingobium aromaticivorans, famous for their atypical gastronomic preferences, as assistants. Originally they were isolated from the ground, flooded with oil, their study showed that they can process a variety of aromatic hydrocarbons for their purposes. Their abilities were enough for lignin.
To adapt bacteria to business, scientists removed three genes from their genome so that one of the intermediate decomposition products, most suitable for humans, became the final one. Having received it, the bacterium sends the result outside and proceeds to a new dose of lignin.
The end result in this study was a compound with the hard-to-pronounce name 2-pyrone-4,6-dicarboxylic acid, fortunately for us better known as PDC. It can be used to synthesize something else, or it can be applied directly. At the moment, the total yield of PDC is 59% of the original mass of lignin, the authors believe that the technology can be improved.
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See an article published in Green Chemistry for details.
Sergey Sysoev
