Lettuce engineered to produce meat proteins

Perhaps you enjoy a burger in a lettuce wrap once in a while—but what if greens were also crucial to the patty? That’s the ultimate promise of new research showing lettuce can be engineered to produce myoglobin, a protein found in meat.

Myoglobin (and its better-known relative hemoglobin) contains the compound heme, the red pigment in blood. Adding heme can give plant-based meat alternatives a meaty flavor and the ability to “bleed.” For example, Impossible Foods uses a compound called leghemoglobin (a heme protein derived from soybeans) to flavor its meat alternatives. But using myoglobin, which is found in animal tissue, could lead to vegetarian products that not only look and bleed like red meat but smell more like it, too.

In the study, published in Frontiers in Plant Science, the researchers describe how they got lettuce and tobacco plants to produce myoglobin for the first time, says lead author Alexia Groff, who worked on the project as a Ph.D. student at Imperial College London. The team engineered the plants’ photosynthesizing chloroplasts—the cell structures that typically turn sunlight into food—to make them do the job.

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing. By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

In previous attempts to make myoglobin using nonanimal sources such as yeast, the protein-production directions were placed in the nucleus’s genome, but Groff and her colleagues found that adding them to the chloroplast genome instead could yield more of it—perhaps producing myoglobin even more efficiently than animals do.

Right now yeast fermentation is the standard method of producing heme (as leghemoglobin), but the sterile environment and industrial equipment necessary for manufacturing can be pricey. Plants are much easier to grow. “Row-crop protein production would likely be faster than fermentation-derived production,” says Adam Leman, a principal scientist at the Good Food Institute, who was not involved in the study. “If existing crop-processing equipment can be used, costs for isolating and purifying a myoglobin-rich fraction could be quite low.”

Lettuce is especially promising: the medium itself is edible, meaning lettuce-produced myoglobin could move more easily through the regulatory steps that can slow down the path from laboratory to market. A more streamlined process could also mean less money spent in production—and far less energy use.

The meat industry is a voracious energy consumer: 60 percent of agricultural energy use comes from farming and transporting animal products. Making meat substitutes less resource-intensive is a step toward more sustainable food systems—even if it means making meat proteins in a vegetable.

“In science, there were things that we used to think were impossible that now are an everyday occurrence,” Groff says. “I’m very excited for what the future of this sector is going to look like.”