Modified yeast turns PET plastic waste into 3D-printed snacks

The chemical composition of a plastic soda bottle and a piece of steak share a fundamental building block: carbon. The challenge has always been that plastic carbon is locked in an inert, synthetic polymer chain that biology cannot touch. Now, chemists from Southern Illinois University (SIU) have demonstrated a way to unlock it, turning polyethylene terephthalate (PET) into edible protein through a process of biological upcycling. The central technical hurdle is that yeast, even genetically modified strains, cannot "eat" a plastic bottle. To bridge this gap, the researchers employ oxidative hydrothermal liquefaction. This process uses water and oxygen at extreme temperatures to shatter the long PET polymer chains into microscopic fragments. Only after this aggressive chemical breakdown does the substrate become bioavailable, serving as a nutrient medium for the reprogrammed yeast. According to biophysicist Aleksey Kornilov, using modified yeast to synthesize complex molecules is a standard biotechnological practice—similar to how insulin is produced. However, the difficulty here lies in the raw material; PET is chemically stubborn and requires rigorous preparation before microbial processing can begin.