Spent grain amounts to as much as 85% of a brewery’s waste. Researchers at Nanyang Technological University in Singapore found a way to convert this brewery waste into a valuable feedstock for yeast. We interviewed Professor William Chen, director of NTU’s Food Science and Technology Programme.

What are the current uses of spent grains as a waste product from breweries?

Currently, spent grains are used mainly for animal feeds.


Can you give an estimate of the size of this waste stream worldwide?

In Singapore alone, more than 23,000 tonnes of spent grains are generated every year.


You developed a process to turn the spent grains into a feedstock to grow beer yeast. How does this process work?

It’s a fermentation process, with food grade and non GM microbes, which break down the macromolecules (lipids, proteins and carbohydrates).


How much of the waste stream can be converted using your process?

Our process contains a second part which allows extraction of cellulose from the post-fermented solid waste. As a whole, there is no waste left behind after fermentation and cellulose extraction.


Has the process already been applied on a production scale?

We are in discussion to make our technology at industry level (more than 100 tonnes scale).


What do you consider to be the main advantages for the brewer?

Sustainable and low cost culture medium for the yeast growth. The surplus yeast culture from our technology can be used for other food applications (bakery for example).


Are there other industrial processes where the conversion process can be applied?

Our technology platform has been successfully applied to our side-streams of food processing industry, including soy bean residues.



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