Scientists grow animal muscle protein in plant chloroplasts for sustainable meat alternatives

Researchers at Imperial College London have demonstrated that plants can be engineered to produce the animal muscle protein myoglobin in their chloroplasts, offering a potentially more sustainable route to a key ingredient for plant-based meat products. The study, published in Frontiers in Plant Science, used a gene gun to insert genes for pig and cattle myoglobin into the chloroplast genomes of tobacco and lettuce seedlings.

Myoglobin is an iron-rich protein responsible for the metallic umami flavor and red color of meat. Because chloroplasts have a bacterial ancestry and exist in high copy numbers per cell, they are generally more efficient at producing large amounts of protein than the cell nucleus. The team confirmed that the inserted genes integrated into the chloroplasts' circular genome and were stably inherited by subsequent generations of both plant species.

For comparison, the researchers also inserted the myoglobin genes into the nuclear genome of tobacco and lettuce, as well as into the chloroplasts of the unicellular alga Chlamydomonas reinhardtii. Measurements using liquid chromatography–mass spectrometry showed myoglobin yields of approximately 800 milligrams per kilogram dry weight in tobacco and 810 mg/kg in lettuce chloroplasts. These yields were at least three times higher than those achieved with nuclear genome insertion in tobacco.

While real meat contains between 8.1 and 11.2 mg of myoglobin per gram dry weight — significantly higher than the plant-derived concentrations — the authors note that plant cultivation is far more resource-efficient than livestock farming. Consequently, plant-derived myoglobin could achieve protein yields per hectare that rival or potentially exceed animal agriculture, with substantially lower water use and greenhouse gas emissions.

The researchers used tobacco as a model plant for technology development and lettuce as an edible crop suitable for future food ingredient production. Dr. Alexia Groff, lead researcher at Imperial College London, explained that the myoglobin could be extracted from leaves and purified using industrial methods. Because it is identical to animal myoglobin, it could be added to plant-based meat products to enhance color, flavor, and nutritional value.

Co-author Dr. Kyoko Morimoto, chief scientific officer at the Cambridge-based plant biotechnology startup Kyomei, added that edible lettuce modified to express myoglobin could potentially serve as a heme-iron-enriched biofortified food, pending legislative approval. The study represents a proof of principle for chloroplast-based molecular farming of animal proteins.

Livestock farming currently requires extensive land for fodder, consumes vast amounts of freshwater, and contributes to global warming through methane and nitrous oxide emissions. The global market for meat alternatives is valued at €6.7 billion to €8.1 billion annually and is projected to grow 8.1% to 12.3% each year over the next decade. Current production methods often rely on microbial engineering in bioreactors, which the chloroplast approach may complement or replace.

The research remains at the proof-of-concept stage. Further work is needed to optimize yields, develop scalable extraction and purification processes, and navigate regulatory pathways for genetically engineered food ingredients. The study was published in Frontiers in Plant Science (2026) with DOI 10.3389/fpls.2026.1876707.