While the ability to achieve significant solubilization of minimally pretreated switchgrass is widespread, they found a five-fold difference between the most- and least-effective biocatalyst—feedstock combinations. The paper, published in Biotechnology for Biofuels, is the most comprehensive comparative study of its type to date, the authors said.

Their analysis demonstrated that under carefully controlled conditions, a microbe called Clostridium thermocellum is twice as effective as fungal enzymes used by industry today. The researchers also tested the different microbes’ performance with minimal pretreatment of the plant materials, indicating it may be possible to reduce or eliminate use of heat and chemicals that make the feedstock accessible to biological processing.

Eliminating both enzyme addition and conventional pretreatment is a potential game-changer.

—Dartmouth engineering professor Lee Lynd, corresponding author

The researchers note that the study was designed to provide indications of intrinsic capability and performance under industrial conditions. They hope their findings will guide the development of advanced processes to lower costs and improve the efficiency of commercial biofuel production.

Although promising, further work is required to translate these results into industrial practice. In particular, the biocatalysts we found to be most effective at solubilizing biomass are non-model microorganisms for which limited molecular tools are available and extensive development and testing under industrial conditions are required, e.g. with respect to solids loading. In addition, optimization, innovation, and evaluation pursuant to a diversity of co-treatment strategies in conjunction with these biocatalysts have yet to be undertaken.

—Paye et al.

The research team also considered the use of mechanical disruption techniques such as milling to complement the microorganisms’ biological breakdown.

Coauthors are Dartmouth College’s Lee Lynd, Julie Paye, Anna Guseva and Sarah Hammer; the National Renewable Energy Laboratory’s Erica Gjersing, Mark Davis, Jessica Olstad, Bryon Donohoe; ORNL’s Brian Davison; Thanh Yen Nguyen and Charles Wyman of the University of California, Riverside; and University of Georgia’s Sivakumar Pattathil and Michael Hahn.

BESC is a Department of Energy Bioenergy Research Center supported by DOE’s Office of Science.

Resources

• Julie M. D. Paye, Anna Guseva, Sarah K. Hammer, Erica Gjersing, Mark F. Davis, Brian H. Davison, Jessica Olstad, Bryon S. Donohoe, Thanh Yen Nguyen, Charles E. Wyman, Sivakumar Pattathil, Michael G. Hahn and Lee R. Lynd (2016) “Biological lignocellulose solubilization: comparative evaluation of biocatalysts and enhancement via cotreatment” Biotechnology for Biofuels 20169:8 doi: 10.1186/s13068-015-0412-y