Scientists harvest valuable protein and fiber from spent brewery grain
The brewing of beer produces great quantities of leftover grain, which often ends up being processed into cattle feed. Scientists have developed a new method of extracting the protein and fiber from that waste, however, for use by humans.
Led by Dr. Haibo Huang, researchers at Virginia Polytechnic and State University (Virginia Tech) started with barley grain waste obtained from local breweries. Although the material is known for containing a lot of protein, its high fiber content makes it difficult for people to digest.
The scientists proceeded to subject the waste to a unique wet milling process, which started with the grain being steeped in a mixture of water and the enzyme alcalase. This made the individual grains softer, so that their components could be more easily separated during the actual milling step. As an added benefit, the waste didn't have to be dried first, as it would in a conventional milling process.
By passing the wet-milled grain through a sieve, the researchers ended up with a liquid protein concentrate and the fiber from which it had been extracted. The concentrate – which contained up to 83 percent of the protein that had previously been "locked up" in the grain – could find use in nutritional supplements, or as a more sustainable alternative to the fishmeal currently utilized in aquaculture feed.
The fiber, on the other hand, was found to work as a feedstock in the production of biofuel. Building on a previous study, Huang and postdoctoral researcher Joshua O'Hair treated the fiber with sulfuric acid, which allowed them to break it down into sugars. When those sugars were fed to Bacillus lichenformis bacteria, the microbes produced the compound 2,3-butanediol – among other things, it can be used to make butanol fuel.
The scientists are now attempting to scale the technology up for industrial-capacity use, plus they're looking for less expensive enzymes to utilize in the milling process. Their research is being presented this week via the online spring meeting of the American Chemical Society.
And as interesting side note, two years ago a team at Queen's University Belfast announced a method of converting brewery grain waste into charcoal.