‘Reverse Photosynthesis’ Process Discovered

A team of scientists from the University of Copenhagen in Denmark and Chalmers University of Technology in Sweden has discovered a natural process it describes as reverse photosynthesis.

‘Reverse Photosynthesis’ Process Discovered

Fungi use reverse photosynthesis to access sugars and nutrients in plants. This image shows the rust fungus Aecidium magellanicum growing on the bush Berberis microphylla . Image credit: Jason Hollinger / CC BY-SA 3.0.
“This is a game changer, one that could transform the industrial production of fuels and chemicals, thus serving to reduce pollution significantly,” said Prof. Claus Felby from the Department of Geoscience and Natural Resource Management at the University of Copenhagen, who is senior author of a study published this week in the journal Nature Communications .
In the process of reverse photosynthesis, the energy in solar rays breaks down — rather than builds plant material — as is the case with photosynthesis.
“You take a large sugar molecule to be oxidized; an enzyme called lytic polysaccharide monooxygenase, which is found in many fungi and bacteria; and some chlorophyll-containing green extract from leaves,” the scientists explained.
“Everything is mixed in a test tube and exposed to sunlight. The biomass is then completely or partially broken down.”
“In practice, this means that it becomes easier to break down larger sugar molecules into smaller constituents, which can then be used as clean energy in ethanol production for cars and ships, plastics, biogas, methanol, etc.”
Without sunlight, it would take hours or days to achieve the same transformation. But when exposed to sunlight, the process takes only 5 minutes.
“We use the term ‘reverse photosynthesis’ because the enzymes use atmospheric oxygen and the Sun’s rays to break down and transform carbon bonds, in plants among other things, instead of building plants and producing oxygen as is typically understood with photosynthesis,” said study co-author Dr. Klaus Benedikt Møllers, from the University of Copenhagen’s Department of Biology.
The team does not yet know how widespread reverse photosynthesis is in nature, but there are many indications that fungi and bacteria use reverse photosynthesis to access sugars and nutrients in plants.
“The discovery means that by using the Sun, we can produce biofuels and biochemicals for things like plastics – faster, at lower temperatures and with enhanced energy-efficiency,” said study lead author Dr. David Cannella, from the University of Copenhagen’s Department of Geoscience and Natural Resource Management.
“Some of the reactions, which currently take 24 hours, can be achieved in just 10 minutes by using the Sun.”
Reverse photosynthesis has the potential to break down chemical bonds between carbon and hydrogen — a quality that may be developed to convert biogas-plant sourced methane into methanol, a liquid fuel, under ambient conditions.
As a raw material, methanol is very attractive, because it can be used by the petrochemicals industry and processed into fuels, materials and chemicals.
“Additional research and development is required before the discovery can directly benefit society, but its potential is one of the greatest we have seen in years,” Prof. Felby concluded.