Bacterial glue: The stuff that binds?

A sticky slime secreted by bacteria could soon find its way into a host of wood products, such as plywood and particleboard. Wisconsin scientists discovered the natural adhesive while investigating the fermentation of alfalfa to make ethanol fuel.

Paul Weimer of the Department of Agriculture’s Dairy Forage Research Center in Madison and his colleagues looked at two species of bacteria. Ruminococcus albus lives in the rumina of cows, and Clostridium thermocellum is widespread in the environment. The bacteria cling to the alfalfa’s cellulose fibers and release enzymes that degrade them. A slimy, protein-based secretion from the microbes’ cell walls keeps the bacteria stuck to the fibers.

Weimer and his team wondered whether this natural glue might serve as a wood adhesive. On its own the bacterial slime didn’t hold together wood sheets as well as a conventional petroleum-based resin adhesive does. But when the researchers made a mixture containing 30 percent bacterial glue and 70 percent resin, the resulting adhesive performed just as well as the resin alone. It also withstood moisture, which commonly weakens biological adhesives.

Replacing a portion of the resin with a less-expensive biological adhesive could cut costs. What’s more, unlike petroleum products, bacterial glue derives from a renewable resource. The USDA researchers have applied for a patent on the bacterial glue.

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