......and has come up with a radical approach to turning plants into biofuels by imaging the cell walls of a Zinnia leaf, which contain most of the cellulose and lignin that occur in plants.
Scientists, from Lawrence Livermore, Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, used four separate imaging techniques to examine the cells of the plant Zinnia elegans. Although a detailed three-dimensional molecular cell wall structure of plants is still not really understood, to develop fuels from plant biomass does require an awareness of how cell walls are organized, to help identify the most effective way of deconstructing the walls into their component parts.
With cellulose and lignin now the focus of much biofuel research, the study, published in the journal Plant Physiology [Lacayo et al. J. Plant Physiol. (2010) DOI: 10.1104/pp.110.155242], is timely. Michael Thelen, who led the research, said “The basic idea is that cellulose is a polymer of sugars, which if released by enzymes, can be converted into alcohols and other chemicals used in alternative fuel production. But for this to happen efficiently, we need to find ways to see how this is proceeding at several spatial scales.”
The leaves of Zinnia seedlings are a useful source of single dark green cells with chloroplasts that can be cultured in liquid for a few days at a time. During this process, the cells, called xylem, alter their shape to look like tube-like cells that can carry water from roots to leaves. Xylem cells represent about 70 per cent of the cellulose in plants that can be used in fuel processing.
Under different microscopy approaches, the team visualized single cells in detail, as well as fine-scale organization of cell walls, cellular substructures, and also the chemical composition of single zinnia cells. It is this last factor that showed there was an abundance of lignocellulose.
However, getting at the plant sugars was not easy. The team had to overcome the hydrophobic protection of crystalline cellulose that lignin provides in the cell wall, and lignocellulose are also resistant to common chemicals and are very insoluble.
Team member, Alex Malkin, pointed out that “The capability to image plant cell surfaces at the nanometer scale, together with the corresponding chemical composition, could significantly enhance our understanding of cell wall molecular architecture. A high resolution structural model is crucial for the successful implementation of new approaches for conversion of biomass to liquid fuels.”
Another member of the team, Catherine Lacayo, said “This approach will be useful for evaluating the responses of plant material to various chemical and enzymatic treatments, and could accelerate the current efforts in lignocellulosic biofuel production.”