Scientists at Imperial College London have successfully cultivated animal muscle protein inside lettuce and tobacco plants, offering a potential new method for developing ingredients for plant-based meat.
The research team engineered the plants to produce myoglobin, the iron-rich protein responsible for the red colour and umami flavour of traditional meat.
The breakthrough comes as UK Energy Secretary Ed Miliband has warned that households will need to reduce their meat and dairy consumption to meet environmental targets. Miliband has committed to a legally binding goal to cut the country's carbon emissions by 87 per cent by 2040. Meeting this target will require households to eat 25 per cent less meat and a fifth less dairy.
Genetic engineering in agriculture
Currently, microbial engineering is one of the most common methods for producing meat alternatives. This technique involves inserting animal proteins into the genome of yeast or bacteria for mass production.
The Imperial College London researchers sought to determine whether a similar process could be achieved using plants. They focused on cloning the genes for pig and cattle myoglobin, then used a "gene gun" to physically shoot copies of those genes into the chloroplasts of lettuce and tobacco seedlings.
Researcher Dr Alexia Groff said: "Plants can be engineered to produce the animal protein myoglobin (Mb) in their chloroplasts, the energy factories for photosynthesis. This could provide a more sustainable way to produce an important ingredient for plant-based meat products."
Dr Groff explained the choice of crops: "We used tobacco because it is the best model plant for developing this technology, and lettuce because it is an edible crop that could eventually be used for food ingredient production."
Yields and resource efficiency
The altered seedlings were grown to adulthood and allowed to flower, with their offspring successfully inheriting the myoglobin genes.
Measurements confirmed the plants yielded approximately 800 milligrams of myoglobin per kilogram of tobacco, and 810 milligrams per kilogram of lettuce.
While traditional meat contains around 8.1 to 11.2 milligrams of myoglobin per gram, the researchers noted that plant cultivation is significantly more resource efficient than livestock production.
"Despite this, plant cultivation is far more resource efficient than livestock production," the researchers said. "Plant-derived Mb [myoglobin] could achieve protein yields per hectare that rival or even potentially exceed those of animal agriculture, while also benefiting from substantially lower water use and greenhouse gas emissions."
The team is now working to develop a method for industrial purification. Dr Groff said: "The myoglobin could be extracted from leaves and purified using industrial protein purification methods."
"Since it is identical to animal myoglobin, it could then be added as an ingredient to plant-based meat products to improve their color, flavor and nutritional value," she said.
Industry reaction and lab-grown meat
Prof Derek Stewart, co-director of the National Alternative Protein Innovation Centre at the James Hutton Institute, called the study an "exciting step forward."
He said: "The paper is an exciting step forward proving the concept that plants can be used to make myoglobin, a key meat protein, in a stable and scalable way.
"It is especially encouraging that the protein could be recovered in a form that was properly folded and bound to heme, which matters for meat-like colour and flavour."
The new plant-based method differs from traditional test tube meat cultivated in laboratories. Lab-grown meat is typically made by harvesting regenerative stem cells from the muscle tissue of living livestock. Those cells are cultured in a nutrient soup of minerals and sugars before developing into skeletal muscle inside bioreactor tanks, a process that takes a few weeks.
Dutch scientists created the first lab-grown beef in 2013, serving a test tube hamburger to two food critics at a restaurant in London.
In March 2017, the San Francisco firm Memphis Meats became the first company to successfully grow poultry meat from stem cells.
