Wednesday, May 2, 2007 - 4:00 PM

Bio-based adhesives from residues of consolidated bioprocessing of cellulosic substrates

Paul J. Weimer1, Charles R. Frihart2, Linda F. Lorenz2, and William R. Kenealy3. (1) U.S. Dairy Forage Research Center, USDA-ARS, 1925 Linden Drive West, Madison, WI 53706, (2) U.S. Forest Products Laboratory, USDA-FS, 1 Gifford Pinchot Drive, Madison, WI 53726, (3) Mascoma Corporation, USDA-FS, 16 Cavendish Court, Suite 2A, Lebanon, NH 03766

Anaerobic bacteria (Clostridium thermocellum or Ruminococcus species) that ferment cellulosic materials to ethanol or other low molecular weight products have been proposed to serve as a basis for single-reactor bioconversions of cellulosics in a scheme termed consolidated bioprocessing (CBP).  These bacteria adhere to substrate via several mechanisms, including an exopolysaccharide-rich glycocalyx.  The solid residues from such fermentations (containing bacterial cells, glycocalyx and undegraded fiber) have novel adhesive properties for bonding wood materials, particularly upon combination with conventional phenol-formaldehyde adhesives.  Such residues have the potential to add value to CBP fermentations for ethanol production.  In experiments with CBP fermentations of cellulosics pretreated only by mechanical grinding, adhesive performance was enhanced by increasing the extent of fermentation (which increases the ratio of glycocalyx + cells to undegraded substrate), and by decreasing the particle size of the residue (which results in a more uniform bond with the wood panel).  Consequently, better adhesive performance was observed with more readily ground and easily degradable substrates  (e.g., pure celluloses or alfalfa fiber) than with difficult to grind and less degradable substrates (e.g., soy hulls, switchgrass, or reed canarygrass).  Aqueous slurries of residues from different biomass substrates displayed marked differences in viscosity and in water-absorption capacity that strongly impact their adhesive performance and practical utility.