The first results were promising. The researchers succeeded in growing lettuce plant tissue in a liquid suspension with acetate. This showed that this crop can absorb and process an externally applied carbon source.
When they grew whole lettuce plants (and rice, canola, tomatoes and several other crops) in light with acetate as a supplement, they found that the plants take up the acetate in the tissue. Acetate labeled with carbon-13, a heavy isotope of carbon, could be found in plant amino acids and sugars. This indicates that they can use the substance in various metabolic processes.
But the study did not show that whole plants can grow on acetate alone without sunlight. In fact, the researchers’ experiments with lettuce plants showed that an excess of acetate inhibits the plants’ growth. Jinkerson says his lab is now working on genetically adapting and growing plants that are more resistant to acetate. This is necessary if the team’s method of artificial photosynthesis is to make a significant contribution to plant cultivation and food production.
Emma Kovak, a food and agriculture analyst at the Breakthrough Institute, said the researchers’ findings “are a first step toward a possible use of acetate as a nutrient in indoor plant production.” This could potentially limit the amount of energy required for indoor horticulture if growers need less light as a result. But “great progress still needs to be made” before acetate-assisted plants grow vigorously in low-light conditions, Kovak said.
Evan Groover, who is focusing on genetic modification of plants for better photosynthesis for his Ph.D. in artificial biology at the University of California at Berkeley, agrees. The study “shows that plants can absorb acetate, but it doesn’t prove that it’s really good for them or that they can make food, fuel or medicine with it,” Groover said. To achieve the latter, a ‘complete reprogramming of facilities’ would be necessary, he says.
At the same time, Groover finds the research “exciting”.
“It shows that there are ways that we can potentially get light and carbon in strange, non-terrestrial environments or environments where traditional agriculture is not possible,” he says.
Food for the square
The researchers’ technique may be used for the first time in an extraterrestrial environment. The researchers submitted their concept for artificial photosynthesis to NASA’s Deep Space Food Challenge. That way, research groups with innovative ideas for feeding astronauts during future space missions can earn prize money and recognition. Last fall, the team’s concept was named one of eighteen US Phase 1 winners. In Phase 2, these teams will be asked to build a prototype that actually produces food. The winners will be announced next year.
Winning the competition is no guarantee that the new food production method will actually be used during a future space mission. All sorts of technical details still need to be worked out, said Lynn Rothschild, senior scientist at NASA’s Ames Research Center, who was not involved in the study. Weight is an important factor – and artificial photosynthesis would likely require new equipment to get into space, such as electrolysers and additional solar panels.
However, according to Rothschild, it is important to remain open to the adaptation of an essential biological process such as photosynthesis and its application in space or on Earth. “Maybe it will lead to something we’ve never thought of.”
Jinkerson says his lab is currently working on genetically engineering and breeding plants to be more tolerant to acetate. It will be necessary for the team’s artificial photosynthesis method to support plant growth and food production in a significant way.
Emma Kovak, a food and agriculture analyst at the Breakthrough Institute, says the authors’ findings represent a “first step toward potentially using acetate to help feed plants for indoor production.” It can reduce the energy needed to run indoor farms if it allows growers to reduce indoor light levels. But “massive advances would be needed,” says Kovak, to enable plants to grow robustly using acetate even in low-light conditions.
Evan Groover, a PhD candidate in synthetic biology at the University of California, Berkeley, whose research focuses on genetically engineering plants to improve photosynthesis, agrees. The study “shows that plants can take up acetate, but it’s not proof that they can really thrive on it or meaningfully synthesize food, fuel or medicine,” Groover says. Achieving the latter, he says, would require “complete reprogramming of facilities.”
Meanwhile, Groover says he found the authors’ paper “encouraging.”
“It shows us ways that we might be able to capture light and carbon in strange, non-terrestrial environments or environments where you can’t do traditional agriculture,” he says.
Food for deep space
An extraterrestrial environment may be where the researchers’ technology is first used. The researchers submitted their artificial photosynthesis concept to NASA’s Deep Space Food Challenge, which awards prize money and recognition to groups with innovative ideas for feeding astronauts on long-duration space missions. Last fall, the team’s concept was named one of 18 US-based Phase 1 winners. In Phase 2, these teams must build a prototype that actually produces food. The winners will be announced next year.
Winning the competition is no guarantee that a new food production technology will be flown on a future space mission. Many technical details need to be worked out first, said Lynn Rothschild, a senior scientist at NASA’s Ames Research Center who was not involved in the new study. Weight is a key consideration—and artificial photosynthesis will likely require hauling new equipment, including additional solar panels and electrolyzers, into space.
But Rothschild says it’s worth keeping an open mind about how any effort to redesign a basic biological process like photosynthesis might be applied, in space or on Earth: “The payoff may be something we haven’t imagined yet.”
This article was originally published in English on nationalgeographic.com.