“Cellulose ethanol” production involves the conversion of plant cellulosic biomass into ethanol. The cellulose (chains of glucose molecules) in plant cell walls are broken down (by a process known as “saccharification”) into individual glucose units. The individual glucose molecules are then converted into ethanol by microbial fermentation. Lignin is a chemical substance that tightly wraps the cellulose fibers in the plant cell walls, and acts as a barrier for effective cellulose utilization. The destruction of the “lignin barrier” is one of the challenges in cellulose ethanol production technology. Physico-chemical methods like steam explosion or use of chemicals are commonly used.

Scientists from the U.S. Dairy Forage Research Center (DRFC) are taking an alternative approach to finding solutions for the “lignin barrier”. By understanding lignin formation and structure in plant cell walls, they hope to “provide opportunities to modify lignin composition and content”, probably in “designer” crops specifically planted for biofuels. John Ralph, a chemist at DFRC, has been studying changes in altered lignin structures in transgenic plants, and these studies have provided basic knowledge on how lignin formation occurs in plant cell walls. One of his interesting findings: lignin formation has “metabolic plasticity”; that is, plants have many possible combinations for assembling lignin in plant cell walls from a variety of building blocks. Ralph sees lignin formation as an “evolved solution that allows plants considerable flexibility in dealing with various environmental stresses”. Another researcher from Ralph’s laboratory, Fachuang Lu, has developed a tool for studying ultrafine chemical structure of the entire plant cell wall. Their work is featured in the April 2007 issue of Agricultural Research.

Related Information: Plant cell wall basics: http://genomicsgtl.energy.gov/biofuels/placemat2.shtml.