Less lignin biofuel for more

biopolymer lignin, colored red in the imaged cross-section, plant lends stability.

An international group of researchers wants to change power plants so that the cellulosic biomass without acid treatment can be effectively processed into fuel.

pest or blessing? On biofuels are the ghosts. For years, more and more food crops are angbaut just to get out of their fruits – such as corn – to make fuels. Leaves and stems, however, remain unused. Especially the solid lignin, which constitutes a major part of the plant in addition to the cellulose, so far prevented an economic re-use of the remaining biomass. An international group of researchers wants to change this with genetically modified plants. They could facilitate the production of cellulose-based fuels.

cellulose and lignin together make up about 80 percent of the mass of plants. Unlike lignin, a biopolymer of alcohol compounds, can the long-chain cellulose molecules break down into usable sugar. In order to separate them from lignin, treat biofuel producers currently before the plant residues with acid. Because this is only possible with special acid-resistant plants, the method is still relatively expensive.

The research team has however in Arabidopsis – identified a gene that is essential for the formation of lignin – a frequently used experimental plant in laboratories. The gene encodes the so-called CSE enzyme. If you switch off the gene, the plant produces no CSE and consequently much less lignin.

Then the cellulose can effectively solve out without acid treatment. About 80 percent of cellulose, the researchers were able to gain from the biomass. In comparison, plants with the major gene for lignin, the proportion of leachable acid cellulose without the new approach was only 18 percent

From a commercial use but is still far away.. First, the researcher must demonstrate that it is feasible for integrated power plants from which cellulosic ethanol can be made. These include switchgrass and poplar. At least they had already found out that the lignin production in these plants is based on a similar cell metabolism.

The genetically modified thale cress, however, shorter than their natural counterparts. This is not surprising: lignin is deposited in the walls of plant cells and makes them more stable. The less there is of this structure in the plant material, the weaker fall from their growth.

Researchers at Lawrence Berkeley National Laboratory recently succeeded but to alter the lignin content of plants targeted so that only certain parts have less lignin. The plants subsequently grew normally. This approach could also work in their plant experiments, says Wout Boerjan by the Flemish Institute for Biotechnology VIB, who was involved in the current study.

Some companies have even begun to experiment with modified plants to bypass the acid separation of lignin and cellulose. The California company wants to reap about Ceres and test the first lignin-poor plants in the fall. Falls off the acid treatment, also not as many enzymes as before are needed to break down the cellulose into sugar, says CEO Richard Hamilton. He expects thus a cost savings of one dollar per gallon of ethanol (3.8 liters).

The Paper:
Vanholme, Ruben et al. “Caffeoyl shikimate esterase (CSE) Is an Enzyme in the Biosynthetic Pathway lignin”, Science , published online on 08.15.2013 (Abstract)

<- googleoff: all ->