Brewing waste: The solution to sustainable fashion?

Polyester and cotton fabrics fill today’s wardrobes. But environmental concerns such as water use and microplastics pollution have revived interest in alternative textiles. In the search for sustainable fabrics, researchers at Pennsylvania State University turned to beer. Or rather the yeast used in its brewing. The team extracted proteins from spent beer-brewing yeast and spun them into strong textile fibers that avoid the environmental impact of petroleum-based polymers, and the ethical as well as land- and water-use concerns of cotton and wool (Proc. Natl. Acad. Sci. U.S.A. 2025, DOI: 10.1073/pnas.2508931122).The biobased fibers should fully dissolve in soil and oceans, says Melik Demirel, a materials scientist who led the work. They should also be cost competitive with natural and synthetic fibers when made at large scale. “Sustainability is one aspect, but the price is a much more important aspect,” Demirel says. “If you don’t meet the price metric, [that is] the biggest limitation in . . . entering the market.”Demirel’s group previously used genetically modified bacteria and yeast to produce proteins found in squid ring teeth and used those to make fibers and other biomaterials. But the process is complex and costly. “In precision fermentation, every condition is set and you are expressing one protein,” he says. In addition, the yeast has to be fed sugar, “which is not cheap at large scale, and you are also tapping into food sources.” So Demirel and colleagues switched to spent yeast—a by-product of the beer, wine, and pharmaceutical industries—as their protein source. They