Solid residues from Ruminococcus cellulose fermentations as components of wood adhesive formulations

Residues from the fermentation of cellulose by the anaerobic bacteria Ruminococcus albus (strain 7) or Ruminococcus flavefaciens (strains FD-1 or B34b) containing residual cellulose, bacterial cells and their associated adhesins, were examined for their ability to serve as components of adhesives for plywood fabrication. The residues contained differing amounts of protein (0.4-4.2% of dry weight), but the ratios of monosaccharides recovered following two-stage treatment of the residue with detergent (pH 7) and TFA were similar for all three strains (0.71 glucose:0.18 xylose:0.08 mannose:0.02 galactose), suggesting similarities in exopolysaccharide composition. Three-ply aspen panels prepared with fermentation residues (FR) displayed better shear strength and wood failure under dry conditions than following a vacuum/pressure/soak/dry treatment, but adhesive properties were inferior to those prepared with conventional phenol-formaldehyde (PF) adhesives. However, panels prepared by incorporating the R. albus 7 FR into PF formulation, at 73% by weight of the total adhesive, exhibited shear strength and wood failure similar to that obtained with PF adhesive alone. Use of residues from fermentations by these bacteria as components of adhesives may add value to biomass fermentations aimed primarily at producing ethanol and other chemical products.