- Written by Urs Fischer & Anna Strom
Because of their wide range of applications in natural and synthetic materials, polymers* are a favourite target for research among bioenergy scientists. Great efforts have gone into trying to separate the desirable cellulose--a (polysaccaride) carbohydrate that is a main component in paper and other materials based on woody biomass--from other, less malleable polymers contained in the walls of tree cells, such as lignin.
Hybrid aspen, of the Populus family, has been chosen for its versatility in terms of tree properties. Moreover, B4E scientists have taken part in mapping its genome.
Describing the new line of research during an annual gathering for researchers of the Umeå Plant Science Centre, at Umeå, Sweden, UPSC post-doctoral researcher Melissa Roach said that the new strategy had been tested as an early step to designing a method with which to control tree cell-wall polymer concentrations.
To do so, scientists at UPSC had designed new trees growing in a hot house, in Sweden, which would be instrumental to the Centre's work to lay bare the best way, in future, to engineer an aspen tree with a view not only to render a malleable raw material (or "feedstock") based on which to make products on a large scale, but also to ensure, as far as possible, that it could be turned into environmentally-sound end products.
Changing the balance between the polymers lignin and cellulose had brought some unexpected results, suggested Roach who is a member of an UPSC team headed by B4E Feedstock platform leader Björn Sundberg and UPSC colleague Totte Niitylä.
"We looked at some key enzymes... to understand their function" and involvement in tree metabolism, Sundberg said. "We saw that they had very different mechanical properties. The trees we made are quite interesting from a research perspective. There is a lot to learn from this".
He added that two separate scientific articles would be published within six month based on his team's discoveries, describing what the scientists had found.
Sugar in, cellulose out
For his part, B4E scientist Johannes Hanson described his group's work to refine an alternative method for "shunting" plant sugars into cellulose.
The group had identified a genetic switch by means of which the scientists could shape the sugar metabolism, he revealed. They were trying to find out to what extent such changes could interfere with plant growth. In a next step, the group would try to find ways to apply the method to specifically to trees.
Hanson joined B4E in spring 2011 as a researcher on the Feedstock Platform, affiliated with UPSC. He is shifting his activities from Utrecht University, where he has been coordinating the Metabolic Reprogramming of Induction Transcription, or Merit, network of plant biologists interested in this field.
Hanson will be working closely with Sundberg and Urs Fischer, with their triple affiliation with B4E, UPSC and the University of Agricultural Sciences.
'Better' wood fibers
In a separate presentation 30 August, Fischer outlined the discovery of two genetic switches which govern enzymes and early signals required for the formation of wood fiber cells. Trials were underway to transfer such genes into hybrid aspen trees with the aim of modulating the wood properties of a sample population, he said.
“While during the last two decades a great effort was made to understand the basics of secondary cell wall formation in the tiny weed Arabidopsis thaliana, it seems now the time has come to transfer such knowledge to trees in order to improve the feedstock for bioenergy production”, said Fischer, who is a B4E spokesperson for the Feedstock Platform.
*Wikipedia.org said 1 September that a polymer is a “large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds”. In a covalent bond atoms share electron pairs. “Although the term 'polymer' is sometimes taken to refer to plastics, it actually encompasses a large class comprising both natural and synthetic materials with a wide variety of properties”, according the widely-used online encyclopedia.