Unusual microbes that can make products from thin air
Marine purple photosynthetic bacteria from the world's oceans have the potential to produce fertilizers and other industrially useful materials with minimal environmental impact.
Researchers hope to make fertilizers for crops through fixation of atmospheric carbon and nitrogen.
Marine bacteria could be harnessed to manufacture useful biopolymers on an industrial scale by taking carbon dioxide and nitrogen from the air, say scientists*１. These biopolymers might be used to produce fertilizers, feed for farmed fish, and even artificial spider silk*2.
That’s the vision behind an ambitious project in Japan involving industry, academia and government partners.
“We will strive to realize the transformation of carbon dioxide and nitrogen into materials such as fertilizers and plastics, based on the analytical and measurement technologies we have cultivated,” says Masatoshi Takahashi of the Future Strategy Department of Shimadzu Corporation, a manufacturer of precision analytical instruments, based in Kyoto, Japan. “We believe our analytical and measurement technology will help realize environmentally friendly manufacturing.”
Harvesting the air
In recent years, there has been a lot of interest in using microorganisms as biofactories to mass produce materials for areas such as renewable energy and functional foods. An intense area of focus is on microbes that use atmospheric carbon dioxide as a raw material, and which might help realize a dream of carbon-negative biomanufacturing.
Takahashi is convinced that this is where the future lies. “As a company, we see it as a very promising market,” he says. “In order to achieve this goal, we will introduce various analytical instruments and related technologies, such as whole organic carbon meters and gas chromatographs, which will help us to select the most suitable bacteria for producing useful substances and to examine culture conditions.”
Shimadzu’s Total Organic Carbon Analyzer.
What sets this project apart, however, is that it uses nitrogen as well as carbon. “There are many efforts to use photosynthetic bacteria to fix carbon dioxide from the air,” notes Takahashi. “But one of the key reasons we joined the project was unparalleled use of carbon dioxide and nitrogen in the air as resources for manufacturing.”
Taking nitrogen from the air and forming nitrogen containing-compounds such as ammonia could help to produce nitrogen-containing fertilizers for agriculture in a more sustainable way than current methods.
“Fertilizers are conventionally made by chemical synthesis using fossil fuels and large amounts of electricity, so their manufacture has a large environmental impact,” says Takashi Ono, of Shimadzu’s Research Promotion Department. “By directly fixing nitrogen in the atmosphere using microorganisms, we hope to produce fertilizers with a low environmental impact. We need to establish new analytical measurement methods that have not been considered before.”
Purple bacteria
The key to achieving this is a marine purple photosynthetic bacterium called Rhodovulum sulfidophilum, which uses seawater as a medium from which to absorb both carbon dioxide and nitrogen.
Keiji Numata, a professor in material chemistry at Kyoto University is leading the research and development of this marine purple photosynthetic bacterium.
His team is studying biopolyesters and polypeptides to find the correlation between the structure and physical properties of various biopolymers, including marine purple photosynthetic bacteria, and using them as practical materials.
Shimadzu has participated in the Japanese government’s carbon dioxide reduction project led by Numata since 2021, and provides analytical equipment necessary for monitoring culture systems, such as a total organic carbon meter and a gas chromatograph. Shimadzu has also established a method for deriving carbon dioxide and nitrogen fixed by purple photosynthetic bacteria using a total organic carbon meter equipped with a nitrogen analysis function.
A start-up company from Kyoto University called Symbiobe Corporation is also participating in the project. Symbiobe is primarily engaged in the construction and commercialization of plants for the production of purple photosynthetic bacteria.
Scaling up
One of the biggest challenges for commercialization is scaling up the culture process from the laboratory to an industrial scale. As a first step towards this goal, the team has recently succeeded in scaling up production to 4,000 litres with a demonstration plant at Kyoto University.
The demonstration plant will operate 24 hours since it uses a combination of natural light and LED lighting that emits light in the wavelength range used by the bacteria. It will contain a seawater-based culture that is seeded with purple photosynthetic bacteria. Then, by blowing carbon dioxide and nitrogen gas into a seawater culture with purple photosynthetic bacteria and circulating it, large-scale cultivation is possible.
Real-time monitoring
The data obtained by Shimadzu’s analytical instrumentation and related techniques will help researchers at Kyoto University and Symbiobe to further improve and evolve cultivation of the marine purple photosynthetic bacteria. Researchers at Shimadzu have found an easy and quick way to measure nitrogen as well as carbon fixation in marine photosynthetic purple bacteria.
Feed for fish farms is another application for materials made from carbon and nitrogen fixation.
“We have also made it possible to measure the carbon-to-nitrogen ratio, an indicator of organic fertilizers, by appropriate pretreatment even if the sample is solid,” says Ono. “This means information about the carbon-to-nitrogen ratio of marine purple photosynthetic bacteria in culture conditions can be fed back to production, and quality can be measured at an early stage, thereby realizing one of the functions required for the practical application of mass-production plants.”
“Such evaluations will be useful in optimizing culture and growth conditions for marine photosynthetic purple bacteria,” adds Masaaki Ota, a senior expert in Shimadzu’s Future Strategy Department. “We’re now fully utilizing our analytical and measurement technology to further improve the carbon dioxide and nitrogen fixation capacity of marine photosynthetic purple bacteria at this demonstration plant.”
Shimadzu has taken the first step to contribute to the realization of sustainable solutions by utilizing its know-how in analytical and measurement equipment. “We will continue to work to create new businesses that contribute to reducing environmental impact,” says Ota.
References
- Higuchi-Takeuchi, M. et al. PLoS ONE 11, e0160981 (2016).
- Foong, C. P. et al. Comm. Biol. 3, 357 (2020).
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