Beer waste is separated into protein for food and fibre for biofuels.

The beer-making process produces the same result for both home brewers and major manufacturers: mountains of wasted grain. After the flavour has been removed from barley and other grains, a protein- and fiber-rich powder is left, which is often utilised in cow feed or disposed of in landfills. Scientists have discovered a novel approach to extract protein and fibre from brewer's leftover grain and use it to make new protein sources, biofuels, and other products.

The researchers will report their findings at the American Chemical Society's spring meeting today (ACS).

The project's chief investigator, Haibo Huang, Ph.D., adds, "There is a significant need in the brewing sector to reduce waste." His team collaborated with local breweries to find a way to turn unused grain into useful products.

"Spent grain has a very high protein content compared to other agricultural waste," says Yanhong He, a PhD student who will present the results at the symposium. Huang and He are both students at Virginia Polytechnic Institute and State University (Virginia Tech).

Craft brewing is more popular than ever in the United States.
This increased demand has resulted in a rise in production, resulting in a significant increase in brewery waste, 85 percent of which is spent grain.This byproduct contains up to 30% protein and up to 70% fibre, and while cows and other animals can digest it, humans find it difficult to digest due to the high fibre content.

Huang and He devised an unique wet milling fractionation procedure to separate the protein from the fibre in order to turn this waste into something more useful. The new method is more efficient than earlier methods since the researchers do not have to dry the grain first.
They put three commercially available enzymes to the test in this process: alcalase, neutrase, and pepsin, and discovered that alcalase treatment gave the best separation without losing a lot of either component. The outcome was a protein concentration and a fiber-rich product after sifting.

The protein concentration collected up to 83 percent of the protein in the discarded grain. Initially, the researchers advocated using the recovered protein to feed farmed shrimp as a less expensive and more sustainable alternative to fishmeal. Huang and He have just begun to investigate using the protein as an ingredient in food products, in response to customer demand for alternative protein sources.

However, the residual fiber-rich product was still left without a defined use. Huang's postdoctoral researcher Joshua O'Hair, Ph.D., discovered a new Bacillus lichenformis species in a spring in Yellowstone National Park last year. The bacteria could convert different carbohydrates to 2,3-butanediol, a chemical that is used to manufacture a variety of products, including synthetic rubber, plasticizers, and 2-butanol, a fuel, according to the study. So He used sulfuric acid to pre-treat the recovered fibre before breaking it down into sugars from cellulose and hemicellulose. The sugars were then fed to the bacterium, which produced 2,3-butanediol.

To keep up with the volume of leftover grain created by breweries, the team wants to scale up the process of separating the protein and fibre components. They're also collaborating with colleagues to establish the separation process's economic feasibility, as the enzymes now employed to separate the protein and fibre components are costly. Huang and He seek to find appropriate enzymes and green chemicals to make this process more sustainable, scalable, and cost-effective.