Accelerating efforts towards lignocellulosic biofuel production
Zinnia elegans
Zinnia elegans:
Zinnia is a common garden annual plant with solitary daisy like flower heads on long stems and sandpapery, lace shaped leaves. The leaves of seedlings provide a rich source of single cells that are dark green with chloroplasts and can be cultured in liquid for several days at a time. During the culturing process, the cells change in shape to resemble the tube-like cells that carry water from roots to leaves. Known as xylem, these cells hold the bulk of cellulose and lignin in plants, which are both major targets of recent biofuel research.
Lignocellulosic biomass refers to plant biomass that is composed of cellulose (23-53%), hemicellulose (20-35%), and lignin (10-25%). Cellulose is biosynthesized in plant cells by joining molecules of glucose (a simple sugar) into long chains through a process called polymerization. The plant then assembles these chains of cellulose into sheets. It is cellulose in lignocellulose that has potential for the production of fuel-grade ethanol by direct fermentation of the glucose. However, enzymatic hydrolysis of lignocellulose and raw cellulose into glucose is hindered by the presence of lignin. The enzyme called cellulase, which hydrolyzes cellulose to glucose, becomes irreversibly bound to lignin.
Accelerating efforts towards lignocellulosic biofuel production
In order to successfully implement new approaches for conversion of biomass to liquid fuels a thorough understanding of the detailed three-dimensional molecular cell wall structure of plants is essential. Michael Thelen from the Lawrence Livermore National Laboratory says, “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.” Alex Malkin, an expert in atomic force microscopy, also from Lawrence Livermore National Laboratory says, “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.”
In order to enhance their understanding of the molecular structure of cell walls a team led by Michael Thelen, in collaboration with researchers from Lawrence Berkeley National Lab and the National Renewable Energy Laboratory, has used four different imaging techniques to reveal the structure of plant cell surfaces at the nanometer scale, of Zinnia elegans. The team was able to visualize single cells in detail – their cellular substructures, fine-scale organization of the cell wall, and even chemical composition of single zinnia cells, indicating that they contain an abundance of lignocellulose.
It was Catherine Lacayo, a postdoctoral scientist working with Thelen and Malkin who came up with techniques that reveal the inner structure of cell walls in these single xylem cells, which represent about 70 percent of the cellulose in plants that can be used in fuel processing. “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.”
Source: https://publicaffairs.llnl.gov/news/news_releases/2010/NR-10-07-03.html
July 20, 2010