Scientists have genetically engineered a close relative of the tobacco plant to pump out nutrients found in human breast milk.
The technology could pave the way for infant formula milk that more closely replicates health benefits of breastfeeding, according to the team behind the work. The study demonstrated that the genetically modified Nicotiana benthamiana could produce complex sugars called human milk oligosaccharides (HMOs) that boost healthy gut bacteria and have benefits for the infant immune system.
Dr Patrick Shih, a plant and microbial biologist who led the work at the University of California, Berkeley, said: “Imagine being able to make all the human milk oligosaccharides in a single plant. Then you could just grind up that plant, extract all the oligosaccharides simultaneously and add that directly into infant formula. There would be a lot of challenges in implementation and commercialisation, but this is the big goal that we’re trying to move toward.”
Breast milk contains about 200 different HMOs, and they are the third most abundant solid component of human milk. They are indigestible for the nursing infant, but serve as food for bacteria that colonise the gut during the first weeks of life. By promoting healthy gut bacteria, there is evidence that HMOs reduce the risk of viral and bacterial infections and they may have other health benefits.
Currently, a small handful of HMOs can be manufactured using engineered E coli bacteria and major manufacturers are starting to incorporate them as an ingredient. But many HMOs remain difficult or impossible to produce in this way and isolating the beneficial molecules from other toxic byproducts is a costly process, so only a limited number of baby formulas include them.
In the latest study, published in the journal Nature Food, the scientists reprogrammed the plants’ sugar-making machinery that is responsible for linking together simple sugars, called monosaccharides, into the vast arrays of branched chains that make up complex sugars. The scientists inserted genes designed to produce specific enzymes that are required to assemble basic sugars into a variety of HMOs. The genetically modified plants produced 11 known HMOs.
“We made all three major groups of human milk oligosaccharides,” Shih said. “To my knowledge, no one has ever demonstrated that you could make all three of these groups simultaneously in a single organism.”
This included a compound called LNFP1, which has been associated with infants having fewer infections, but cannot be made in large quantities using microbial fermentation methods. Shih and colleagues said the approach could lead to healthier and more affordable formula for babies, or more nutritious non-dairy plant milk for adults. Other scientific teams are investigating the potential for HMO-based medicines.
Shih said: “This could enable not just improved plant-based milks for infants but also for many other facets of adult diet and health. Plants have already been engineered to produce oils and fatty acids that are better for our health. These are just a few of a growing list of ways we can start making designer plants that are tailored to improve human health.”
