Joseph Keddie and his team at the University of Surrey have cracked a problem that has quietly plagued wastewater treatment for years: bacteria die during the very process meant to save them. Now, by adapting a technique borrowed from latex glove manufacturing, the researchers have figured out how to keep bacteria alive 500 times better than conventional methods—and in doing so, they've opened the door to a fundamentally different way of cleaning our water.
The challenge is deceptively simple. Wastewater treatment already depends entirely on bacteria to break down organic matter and process nitrogen compounds, but those microorganisms are grown in massive, open tanks that consume space, cost money, and respond sluggishly when treatment demands shift. The promise of biocoatings—thin polymer layers embedded with living bacteria—is to pack far more bacterial activity into far less space, potentially transforming how we handle sewage and industrial waste. The catch: standard manufacturing methods kill nearly all the bacteria in the process.
Conventional approaches dry the coating in warm air after it's made. That sounds innocent enough, but to bacteria it's catastrophic. The heat and drying strip water from their cells and concentrate salts to toxic levels. Most species simply cannot survive it. The Surrey team, working with researchers at the University of Warwick and including Ph.D. students Alexia Beale and Kathleen Dunbar, decided to flip the entire process on its head. Their method, published in ACS Applied Materials & Interfaces, never dries the coating at all.
Instead, they adapted an industrial technique used in latex glove production. A substrate is first coated with calcium salt, then dipped into a liquid mixture containing bacteria and polymer particles. Where the salt is present, the polymer gels instantly, forming a thick, porous layer around the bacteria. Here's the crucial step: that layer is immediately submerged in warm lysogeny broth—a nutrient-rich liquid routinely used to grow bacteria in laboratories—rather than shoved into an oven. The warmth causes the polymer particles to fuse together, creating a hard but permeable coating. The bacteria, meanwhile, stay submerged and hydrated throughout. They are never exposed to air.
The results speak for themselves. Not only do the bacteria survive at vastly higher rates, but they also remain metabolically active—meaning they can actually do the work they're designed for. When the researchers supplied the coated bacteria with glucose, they produced ethanol through fermentation, proving the concept works for biofuel generation. The team is already exploring hydrogen production as a next application.
The porous structure of these new coatings matters as much as the manufacturing technique itself. Bacteria inside need nutrients to reach them and waste products to escape. Conventional dried coatings are dense and nearly impermeable. The new coatings have water permeability more than ten times higher, as confirmed by electron microscopy. Dr. Suzanne Hingley-Wilson, a bacteriologist and co-author from Surrey, emphasizes what this unlocks: the method works for desiccation-intolerant bacteria—species that cannot withstand any drying and have been entirely locked out of conventional biocoating processes until now. Suddenly, a whole range of bacterial species becomes available for environmental and industrial applications.
For wastewater treatment systems already operating around the world, the implications are significant. Biocoatings could be applied to carriers inside existing treatment plants or mounted on modular panels that slip into current infrastructure, concentrating bacterial power without requiring expensive new facilities. It's an elegant example of how rethinking a single manufacturing step can unlock capabilities that seemed impossible before.