Engineered yeasts help turn PET plastic and crop waste into protein-rich cookies

From plastic bottle to cookie

Plastic might be the last ingredient you would expect in a cookie recipe, but a team of researchers is working to change that. Scientists at Southern Illinois University (SIU) Carbondale have programmed yeasts to transform plastic and agricultural waste into edible proteins and flavoring molecules, creating protein-rich cookies from materials that would otherwise be discarded.

The technology, presented at the American Chemical Society's Fall 2026 meeting in Chicago, could offer a new approach to plastic upcycling while potentially supporting food production in resource-limited environments. The work forms part of a NASA-led project exploring food technologies for deep-space missions.

"We were trying to develop technologies for plastic upcycling to make more valuable products," said Associate Professor Lahiru Jayakody. "We thought, why not focus on making food? Because plastic is carbon and food is carbon."

The science behind µBites

The cookies are called µBites, pronounced "microbites." The team focused on polyethylene terephthalate (PET), one of the most widely used plastics and a common material for drinks bottles. PET contains carbon-rich molecules that could potentially be converted into components of food.

Rather than relying on chemical reactions and solvents to carry out the transformation, the researchers used genetically programmed yeasts as biological production systems. Jayakody and graduate student Sandhya Jayasekara programmed several types of yeast, including baker's yeast, to convert molecules derived from plastic and agricultural waste into proteins, vitamins and flavoring compounds.

"Microbes are very clever, so we are using their traits to solve the problems we created," Jayakody said.

The process begins with oxidative hydrothermal dissolution, a method developed by SIU Carbondale Geology Professor Ken Anderson that uses water and oxygen at high temperatures and pressures to break down PET and agricultural biomass into a liquid feedstock. The yeast then converts this feedstock into nutritious food slurries, which are 3D-printed into disc-shaped cookies and hardened, often in a microwave.

From space missions to disaster zones

The research originated as part of NASA's Deep Space Food Challenge, which invited scientists to develop new food technologies for long-duration spaceflight. A round-trip to Mars would take about three years, Jayakody noted, making resource efficiency critical.

"When an astronaut goes to Mars, they have to survive in extreme conditions," he said. "You have to use everything you have."

Beyond space, the µBites system is designed to be portable and tunable, with potential applications in submarines, disaster relief vehicles, deserts, the Arctic and the Antarctic. "These units could be deployed in submarines or disaster relief vehicles to produce on-demand, on-site food," Jayakody told ScienceAlert.

Safety and sensory testing

The team has not yet eaten the cookies themselves. "We haven't eaten them yet because we're awaiting approval for testing in humans," Jayakody said ahead of the ACS presentation. The researchers report that the cookies "receive high marks on aroma," and blind sensory tests have yielded positive responses to smell and a pleasing texture.

Safety analysis has been conducted through accredited third-party laboratories, checking for toxic chemicals, heavy metals, allergens and pathogens, along with simulated digestive studies. The cookies currently cost about $60 a kilogram to produce, a figure the team hopes to reduce.

Efficiency and future directions

The process takes one to two days to complete and currently converts more than 50% of the carbon from waste materials into food products, with about 10% ending up as waste gas or unconverted carbon. The team aims to approach 100% recirculation of unconverted carbon, aligning with a zero-waste concept.

A major hurdle is microgravity, as the system must operate in the absence of gravity, but the design is intended to work in such conditions.

The byproducts of the process could also be used to produce milk alternatives and meat alternatives. The researchers are exploring feed manufacturing as well, and they hope the cookies could eventually be consumed by the public, potentially within a few years.

Addressing future food demand

The project comes amid projections that global food demand will rise by 35% to 56% by 2050, with about 30% of the world's population at risk of hunger. In this context, turning plastic waste into food offers a dual benefit: reducing waste while providing nutrition in constrained environments.

As Jayakody put it, the work leverages the natural capabilities of microbes to address problems humans have created. "Plastic is carbon and food is carbon," he said, underscoring the underlying simplicity of the concept.

For now, the µBites remain a proof of concept, awaiting human taste tests and further refinement. But the researchers are optimistic that the technology could one day feed astronauts, disaster survivors and perhaps even consumers on Earth.