Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/28/2003
Publication Date: 6/18/2003
Citation: Weimer, P.J., Conner, A.H., Lorenz, L.F. 2003. Fermentation residues from ruminococcus cellulose fermentations as components of wood adhesive formulations. Applied Microbiology and Biotechnology. 63:29-34. Interpretive Summary: Ethanol is currently produced by yeast fermentation of sugars obtained from corn starch. Cellulose is much more abundant in plant material than is starch, but the technology of cellulose conversion to ethanol will require the simultaneous production of additional marketable products if ethanol production from cellulose is to become commercially feasible. Several species of bacteria can ferment cellulose directly to ethanol while also producing a glue that allows them to stick to cellulose fibers. We tested the residue left after cellulose fermentation by several bacteria (which contained leftover cellulose, bacterial cells, and the glue) as a complete or partial substitute for phenol-formaldehyde (PF) adhesive in the fabrication of plywood panels. The fermentation residue alone was inferior to PF, particularly under wet exposure conditions. When mixed with PF, fermentation residue could replace up to 73% of the PF without substantial loss of adhesive properties under both dry and wet exposure conditions. This research provides a second potentially marketable product from the direct microbial conversion of cellulosic materials to ethanol, an emerging technology that may be an alternative to conventional ethanol production from corn.
Technical Abstract: 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 amount of protein (0.4 to 4.2% of dry weight), but the ratio of monosaccharides recovered following two-stage treatment of the residue with detergent (pH 7) and trifluoroacetic acid were similar for all three strains (0.71 glucose : 0.18 xylose : 0.08 mannose : 0.02 galactose). Three-ply aspen panels prepared with fermentation residues 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 fermentation residue 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.