Watching Plant Biomass Breakdown to Improve Biofuel Production

Researchers utilized four microscopy techniques to visualize plant cell walls.

The Science

Sustainable and cost-effective production of biofuels from plant biomass is hindered by the cost of pretreatment and low sugar yields after enzymatic hydrolysis of plant cell wall polysaccharides. Many studies have looked at enzymatic action on individual biomass components, but in nature, the plant cell wall is a complex, networked structure that interacts concertedly with pretreatment enzymes. To fully understand the mechanisms of enzymatic plant cell wall deconstruction for optimal production of bioenergy from biomass, it is imperative to understand the whole system. Scientists at the U. S. Department of Energy’s (DOE) BioEnergy Science Center (BESC) and DOE National Renewable Energy Laboratory (NREL) have addressed this problem by using a combination of advanced microscopic imaging methods in a correlative, real-time manner to examine both fungal and bacterial enzyme systems. With this new technology, they are able to localize the enzymatic sites of action without compromising the cell wall’s structural integrity. Furthermore, high-resolution measurement of the microfibrillar architecture of cell walls suggests that digestion is primarily facilitated by enabling enzyme access to the hydrophobic cellulose face. The results suggest that an optimal strategy for enhancing fermentable sugar yield from enzymatic deconstruction is to modify lignins to be more amenable to removal through pretreatment while maintaining polysaccharide integrity, improving accessibility to enzyme action.


Greater understanding of the mechanisms contributing to chemical and enzymatic solubilization of plant cell walls is critical for enabling cost-effective industrial conversion of cellulosic biomass to biofuels. One of the key challenges in scaling up biofuels manufacturing is development of a cost-effective way to break down cellulose into sugars for subsequent fermentation. This study applied several different types of microscopy to understand the details of how cellulase enzymes perform this task, in the interest of ultimately optimizing the procedure. After lignin removal, fungal cellulases penetrated the remaining cellulose pore structure more efficiently than did bacteria-derived multienzyme complexes. However, this behavior hinges on a lignin extraction scheme that preserves the native architecture of the cellulose.

Principal Investigator

Shi-You Ding
National Renewable Energy Laboratory

BER Program Manager

Kari Perez

U.S. Department of Energy, Biological and Environmental Research (SC-33)
Biological Systems Science Division
[email protected]


Ding, S.-Y., Y.-S. Liu, Y. Zeng, M. E. Himmel, J. O. Baker, and E. A. Bayer. 2012. “How Does Plant Cell Wall Nanoscale Architecture Correlate with Enzymatic Digestibility?” Science 338(6110), 1055–60. DOI: 10.1126/science.1227491. (Reference link).