In the lab, yeast turns plastic waste into protein cookies

A cookie made partly from a soda bottle and a corn stalk sits at the intersection of two stubborn problems: waste and food supply. At Southern Illinois University Carbondale, Associate Professor Lahiru Jayakody, graduate student Sandhya Jayasekara and their colleagues have programmed yeast to turn both into the ingredients for a snack called µBites.

The target is polyethylene terephthalate, or PET — the plastic used in most soda and water bottles. Before the microbes arrive, geology professor Ken Anderson’s process, called oxidative hydrothermal dissolution, uses water and oxygen at high temperature and pressure to break the tough material and plant waste into smaller fragments. Programmed yeast, including ordinary baker’s yeast, then rebuilds those fragments into proteins, fats and acids.

The cookies have not yet undergone formal taste testing. Researchers say the data collected so far indicate that the cookies are safe to eat, while formal taste testing awaits institutional approval. Informal aroma tests have produced positive reactions, with participants saying they would be willing to eat the cookies if food choices were limited.

The yeast is doing more than supplying protein. Jayasekara has engineered one strain to produce vanilla flavoring from plant biomass and another to turn ethylene glycol from PET into beta-carotene, which the body converts into vitamin A. The team mixed the microbial ingredients with fiber, starch and sweetener, then used a 3D printer to form the cookies.

Concretely, the work could give crews in submarines or lunar and Martian outposts a way to make some food ingredients from waste already on hand, rather than relying entirely on conventional supplies. That remains a research-stage possibility: the team still wants microbes to produce the added starch, fiber and sweetener, and Jayakody says public availability could come within a few years. The project was presented at an American Chemical Society meeting, and its food-demand rationale rests on United Nations projections of a 35 to 56 percent rise by 2050.