Science fiction stories imagined future humans living in underground cities on Mars, in hollowed-out asteroids, and on free-floating space stations far from the sun. But if humans are ever to survive in any of those harsh and alien environments, they’ll need ways to grow food using limited resources—and photosynthesis, the highly successful but energy-inefficient process by which plants convert sunlight into sugar, might not cut it. .
Now some scientists are wondering if it is possible to produce food more efficiently by skipping photosynthesis altogether and growing plants in the dark.
The idea sounds as sci-fi as cities on Mars. But a team of researchers took the first step toward realizing a study published in Nature Food in June. The research shows that it is possible to grow algae, edible yeast and mushroom-producing fungi in the dark by treating them with a carbon-based compound called acetate that did not come from plants, but was produced using solar power. Scientists hope that this method, a type of “artificial photosynthesis”, could open up new ways of producing food using less physical space and energy than traditional agriculture – including, perhaps, crops that can grow in the dark.
While other experts are skeptical that it will ever be possible to so radically redesign plant biology, they are excited by the technology the researchers have invented and the team’s idea of how to make food production more efficient.
“We need to find ways to grow plants more efficiently,” said study co-author Feng Jiao, a professor of chemical and biomolecular engineering at the University of Delaware. “Which [solution] is best? I think the beauty of science is that we explore all the possibilities.”
More efficient than nature
With the exception of a few extreme environments such as deep-sea hot springs—sustained by the chemical energy of hydrogen sulfide that erupts from cracks in the seafloor—all life on Earth is powered by the sun. Even predators such as tigers and sharks are part of complex food webs that extend to plants and, in the oceans, to tiny green algae. To see also : Authorities warn of an increase in E. coli infections. These so-called primary producers have a biological superpower: the ability to create organic carbon from carbon dioxide through photosynthesis, a biochemical process powered by sunlight.
But while photosynthesis is necessary for life as we know it, it’s not terribly efficient: only about one percent of the sunlight that hits plants is actually captured and used to produce organic carbon. That inefficiency will be a challenge if humans ever want to establish a self-sustaining presence in space, where it will be vital to produce food using as few resources as possible.
It’s also a problem on Earth today as the human population grows, putting pressure on farmers to squeeze more calories out of the same land.
Some scientists believe the solution is to genetically engineer crops for more efficient photosynthesis. The researchers behind the new study propose something more unusual: replacing biological photosynthesis with a partially artificial process of converting sunlight into food. Their process is a version of artificial photosynthesis, a term that has been around for years and encompasses various approaches to converting sunlight, water and CO2 into liquid fuels and chemicals like formate, methanol and hydrogen. The researchers behind the new study say their work represents the first time an artificial photosynthesis system has been paired with an attempt to grow common food-producing organisms.
Their system is based on electrolysis, or the use of electric current to initiate chemical reactions inside a device called an electrolyzer. In their recent study, the researchers created a two-stage solar-powered electrolyzer system that converts carbon dioxide and water into oxygen and acetate, a simple carbon-based compound.
The authors then fed this acetate to Chlamydomonas reinhardtii, a photosynthetic green alga. They also fed the acetate to nutritional yeasts and mycelium-producing fungi—which don’t photosynthesize themselves, but usually require organic carbon made by plants to grow.
All of these organisms were able to take up acetate and grow in the dark – independent of sunlight or photosynthetically derived carbon.
Compared to photosynthesis, the process was surprisingly efficient. Using artificial photosynthesis, green algae could convert solar energy into biomass about four times more efficiently than crops using biological photosynthesis. Yeast grown using this process was almost 18 times more energy efficient than crops.
“This is one of the key advantages of using man-made roads over natural roads,” says Jiao.
Growing crops in the dark?
Scientists already knew that the alga C. reinhardtii could grow on acetate in the dark—the organism is a mixotroph, meaning it can switch between making its own food photosynthetically or eating organic carbon produced by other plants. See the article : Food truck Friday night at Moncus Lafayette. But according to the study’s senior author Robert Jinkerson of the University of California, Riverside, this is the first time that C. reinhardtii has been grown on acetate that was not created by recent photosynthesis or petroleum derivatives, which are the fossil remains of ancient photosynthesis. That is significant.
“This is the first time that any photosynthetic organism, like an algae or a plant, has grown independently of photosynthesis since they evolved,” says Jinkerson. “It’s completely separate.”
Having grown algae without photosynthesis, the researchers turned to a more difficult question: could they also grow plants?
Their initial results were encouraging. In the dark, the researchers grew lettuce tissue in a liquid suspension containing acetate, confirming that it could absorb and metabolize an externally supplied carbon source.
And when they grew whole lettuce plants in the light (as well as rice, canola, tomatoes and several other types of crops) but fed them extra acetate, they found that the plants incorporated the acetate into their tissue. Acetate labeled with a heavy isotope of carbon, called carbon-13, could be incorporated into amino acids and sugars, suggesting that it could be used by plants to support a variety of metabolic processes.
However, the study did not show that whole plants could be grown entirely on acetate without access to sunlight – in fact, the researchers’ experiments with lettuce showed that too much acetate actually inhibited plant growth. Jinkerson says his lab is currently working on genetically engineering and breeding plants to make them more tolerant to acetate. This will be necessary for the team’s artificial photosynthesis method to support plant growth and food production in a meaningful way.
Emma Kovak, a food and agriculture analyst at the Breakthrough Institute, says the authors’ results represent “a first step toward the potential use of acetate as an aid in feeding plants for indoor production.” It could reduce the energy needed to run indoor farms if it allows growers to reduce indoor light levels. But “a massive advance would be necessary,” says Kovak, to enable plants to grow vigorously with acetate even in low light.
Evan Groover, a doctoral student 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 absorb acetate, but it’s not proof that they’re able to actually thrive on it or meaningfully synthesize food, fuel or medicine,” says Groover. Achieving the latter, he says, would require a “complete reprogramming of the plant.”
At the same time, Groover says he found the author’s work “exciting.”
“It shows us ways we could capture light and carbon in strange, non-terrestrial environments or environments where traditional agriculture can’t be done,” he says.
Food for deep space
An alien environment may be where the explorer’s technology is first applied. The researchers submitted their artificial photosynthesis concept to NASA’s Deep Space Food Challenge, which awards cash prizes and awards to groups with innovative ideas for feeding astronauts on long-duration space missions. Last fall, the team’s concept was named one of 18 U. See the article : Combating food waste and food insecurity through legislation – Food Tank.S.-based Phase 1 winners. In Phase 2, those teams are asked to build a prototype that actually produces food. Winners will be announced next year.
Winning a competition is not a guarantee that a new food production technology will be used in a future space mission. Many technical details would need to be worked out first, said Lynn Rothschild, a senior researcher at NASA’s Ames Research Center, who was not involved in the new study. Weight is a key consideration—and artificial photosynthesis would 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 efforts to redesign fundamental biological processes like photosynthesis might apply, in space or on Earth: “The payoff may be something we haven’t yet imagined.”
