Brewing beer leads to production of many waste streams such as spent grain and spent brewer’s yeast. Efforts have been made to repurpose the brewer’s spent grain for use in animal feed, biofuel production, or simply compost, but in many cases, this spent grain ends up in landfills. However, researchers from Singapore’s Nanyang Technological University have created a process to extract >80% of available protein to create a protein isolate. Around 200 grams of protein can be isolated from 1 kilogram of spent grain. To isolate, the spent grain is first sterilized before being fermented by Rhizopus oligosporus, a fungus commonly used to produce tempeh. This fermentation increases the protein extractability in the grain. The researchers use microwave-assisted three-part partitioning to extract and separate proteins and increase their antioxidant activity. Read more here. In addition to brewer’s spent grain, spent brewer’s yeast is another large waste stream generated during the brewing process.
Spent brewer’s yeast is the leftover dead yeast post-fermentation. This can be used to make marmite and is a common additive in pet food. A recent application used spent brewer’s yeast to filter metals of electronic waste from waste streams. Spent brewer’s yeast can be dried and used to allow metal ions to adsorb to the surface due to electrostatic interactions. Through acid treatment, metals can be removed from the yeast surfaces and then recycled. The yeast can also be reused to recover different metals.
What are your thoughts on the applications for repurposing these brewing waste streams?
Image From: Precision Fermentation