Repurposing proteins from beer-brewing waste

Researchers from Nanyang Technological University, Singapore (NTU Singapore), have created a method for extracting over 80% of the available protein in the solid residue leftover after brewing beer from malted barley — this leftover component is commonly referred to as brewers’ spent grain (BSG).

BSG is claimed to be the most significant by-product of the beer brewing industry, with around 36.4 million tons of it produced globally every year. And while some efforts are made to repurpose it in applications such as animal feed, biofuel production or composting, a substantial portion still ends up in landfills.

Now the new NTU extraction method is designed to provide a way for the protein component from this waste to be repurposed into new products.

Around 200 g of protein can be extracted from 1 kg of BSG using this method. According to the researchers, the BSG proteins are safe for human consumption and of high quality, which makes them suitable for direct use in supplements or for enhancing the protein content of plant-based foods. The extracted proteins were also found to be rich in antioxidants, which could make them suitable for other applications, such as in cosmetics.

The NTU researchers presenting BSG (left), protein powder (middle) and a sample of a moisturising cream (right).

Unlocking the protein

The NTU FST Programme collaborated with Heineken Asia Pacific, the producer of Tiger Beer, using the BSG in the study.

To extract the protein from the BSG, the researchers first sterilised it before using Rhizopus oligosporus, a food-grade fungus commonly used to ferment soybeans to produce tempeh, a soy-based food popular in Southeast Asia. The three-day fermentation process helps break down the BSG’s complex structure, making its protein content more easily extractable.

The fermented BSG is then dried, ground into a powder, sieved and spun in a centrifuge to separate the protein, which would float to the top. Once extracted, the protein could be used for food or cosmetic applications.

(L-R) Director of NTU’s Food Science and Technology (FST) program Professor William Chen and FST Senior Research Fellow Dr Chai Kong Fei, who is holding up a bag of brewers’ spent grain.

Lead author Professor William Chen, Director of NTU’s Food Science and Technology (FST) program, said: “Our method presents an innovative way to repurpose beer waste into a valuable protein source for global nutrition. Beyond mere innovation, our work embodies a narrative of turning what was once considered waste into a vital resource, a symbol of sustainability and a solution to one of humanity’s most pressing challenges: protein scarcity.”

The NTU FST team will be in discussion with Heineken Asia Pacific to scale up their protein extraction method and plans to collaborate with several food and beverage and cosmetic companies to further implement their technology, with an eye towards commercialisation.

The findings were published recently in the peer-reviewed journal Innovative Food Science and Emerging Technologies.

Top image credit: iStock.com/Imladris01