Bi-directional binding and release of hydrogen in bioreactor
A team of microbiologists from Goethe University Frankfurt has succeeded in using bacteria for the controlled storage and release of hydrogen. This is an important step in the search for carbon-neutral energy sources in the interest of climate protection. The corresponding paper has now been published in the renowned scientific journal “Joule".
FRANKFURT. The fight against climate change is making the search for carbon-neutral energy sources increasingly urgent. Green hydrogen, which is produced from water with the help of renewable energies such as wind or solar power, is one of the solutions on which hopes are pinned. However, transporting and storing the highly explosive gas is difficult, and researchers worldwide are looking for chemical and biological solutions. A team of microbiologists from Goethe University Frankfurt has found an enzyme in bacteria that live in the absence of air and bind hydrogen directly to CO2, in this way producing formic acid. The process is completely reversible – a basic requirement for hydrogen storage. These acetogenic bacteria, which are found, for example, in the deep sea, feed on carbon dioxide, which they metabolise to formic acid with the aid of hydrogen. Normally, however, this formic acid is just an intermediate product of their metabolism and further digested into acetic acid and ethanol. But the team led by Professor Volker Müller, head of the Department of Molecular Microbiology and Bioenergetics, has adapted the bacteria in such a way that it is possible not only to stop this process at the formic acid stage but also to reverse it. The basic principle has already been patented since 2013.
“The measured rates of CO2 reduction to formic acid and back are the highest ever measured and many times greater than with other biological or chemical catalysts; in addition, and unlike chemical catalysts, the bacteria do not require rare metals or extreme conditions for the reaction, such as high temperatures and high pressures, but instead do the job at 30 °C and normal pressure," reports Müller. The group now has a new success to report: the development of a biobattery for hydrogen storage with the help of the same bacteria.
For municipal or domestic hydrogen storage, a system is desirable where the bacteria first store hydrogen and then release it again in one and the same bioreactor and as stably as possible over a long period of time. Fabian Schwarz, who wrote his doctoral thesis on this topic at Professor Müller's laboratory, has succeeded in developing such a bioreactor. He fed the bacteria hydrogen for eight hours and then put them on a hydrogen diet during a 16-hour phase overnight. The bacteria then released all the hydrogen again. It was possible to eliminate the unwanted formation of acetic acid with the help of genetic engineering processes. “The system ran extremely stably for at least two weeks," explains Fabian Schwarz, who is pleased that this work has been accepted for publication in “Joule", a prestigious journal for chemical and physical process engineering. “That biologists publish in this important journal is somewhat unusual," says Schwarz.
Volker Müller had already studied the
properties of these special bacteria in his doctoral thesis – and spent many years
conducting fundamental research on them. “I was interested in how these first
organisms organised their life processes and how they managed to grow in the absence
of air with simple gases such as hydrogen and carbon dioxide," he explains. As
a result of climate change, his research has acquired a new, application-oriented
dimension. Surprisingly for many engineers, biology can produce by all means practicable
solutions, he says.
Publication: Fabian M. Schwarz, Florian Oswald, Jimyung Moon, Volker Müller: Biological hydrogen storage and release through multiple cycles of bi-directional hydrogenation of CO2 to formic acid in a single process unit. Joule (2022) https://doi.org/10.1016/j.joule.2022.04.020
Picture download: https://www.uni-frankfurt.de/119545783
Caption: Model of a potential bacterial hydrogen storage system: during the day, electricity is generated with the help of a photovoltaic unit, which then powers the hydrolysis of water. The bacteria bind the hydrogen produced in this way to CO2, resulting in the formation of formic acid. This reaction is fully reversible, and the direction of the reaction is steered solely by the concentration of the starting materials and end products. During the night, the hydrogen concentration in the bioreactor decreases and the bacteria begin to release the hydrogen from the formic acid again. This hydrogen can then be used as an energy source.
Professor Volker Müller
Department of Molecular Microbiology & Bioenergetics
Institute for Molecular Biosciences
Goethe University Frankfurt
Tel.: +49 (0)69 798-29507
Team from Goethe University contributes to article in “Nature”
Atmospheric researchers from the international CLOUD consortium have discovered a mechanism that allows nuclei for ice clouds to form and rapidly grow in the upper troposphere. The discovery is based on cloud chamber experiments to which a team from Goethe University contributed highly specialised measurements. Although the conditions for nucleus formation are only fulfilled in the Asian monsoon region, the mechanism is expected to have an impact on ice cloud formationacross large parts of the Northern Hemisphere (Nature DOI 10.1038/s41586-022-04605-4)
FRANKFURT. The Asian monsoon transports enormous amounts of air from atmospheric layers close to Earth's surface to a height of around 15 kilometres. Like in a gigantic elevator, human-induced pollutants also end up in the upper troposphere in this way. A research team from the CLOUD consortium (Cosmics Leaving Outdoor Droplets), including atmospheric researchers from Goethe University in Frankfurt, have reproduced the conditions prevailing there, among them cosmic radiation, in their experimental chamber at the CERN particle accelerator centre in Geneva.
In the process, they identified that up to 100 times more aerosol particles form from ammonia, nitric acid and sulphuric acid than when only two of these substances are present. These particles are then available on the one hand as condensation nuclei for liquid water droplets in clouds and on the other hand as solid seeds for pure ice clouds, so-called cirrus clouds. The research team also observed that ice clouds with the three-component particles already form at lower water vapour supersaturation than anticipated. This means that the ice clouds already develop under conditions that atmospheric researchers worldwide had so far assumed did not lead to the formation of cirrus clouds. With model calculations from around the globe, the CLOUD research team was also able to show that the cloud nuclei can spread across large parts of the Northern Hemisphere within just a few days.
“The experiment in the cloud chamber was a reaction to the results of field experimentsover Asia. These measurements showed that ammonia is present there in the upper troposphere during the monsoon," explains Professor Joachim Curtius from Goethe University. “Previously, we had always assumed that ammonia, due to its water solubility, was rinsed out of the rising air masses before it reached the upper troposphere." As the CLOUD researchers' experiment now corroborates, ammonia is an essential ingredient for more cloud formation. Ammonia emissions in Asia come predominantly from agriculture.
The international CLOUD research collaboration (Cosmics Leaving Outdoor Droplets) is made up of teams from 21 research institutions. In the experiment of which the research team is now presenting the results in the current issue of “Nature", the researchers led by Curtius were responsible for the mass spectrometric measurement of the sulphuric acid concentration. This concentration changed over the course of the experiment, but was still always very low, like in the upper troposphere: for a single sulphuric acid molecule there are over a trillion other gas molecules. “Apart from the very best measuring equipment, such measurements require highly specialised expertise. That is why you need teams with complementary skills to conduct such an experiment," explains Curtius, who is a member of the CLOUD steering committee and was coordinator of the EU project CLOUD-MOTION successfully completed just recently. Like in the atmosphere, sulphuric acid forms in the CLOUD chamber from sulphur dioxide and hydroxyl radicals.
Clouds are an important and at the same time still insufficiently understood element of global climate. Depending on whether they float high up or low down, their water or ice content, how thick they are or over which region of the globe they form, it gets warmer or colder beneath them. To improve the precision of climate models, researchers worldwide require exact knowledge of all the processes surrounding clouds as a climate factor. The CLOUD research team's findings are helping them a long way towards increasingly reliable climate predictions.
Publication: Mingyi Wang et al., Synergistic HNO3 H2SO4 NH3 upper tropospheric particle formation. Nature https://www.nature.com/articles/s41586-022-04605-4, DOI 10.1038/s41586-022-04605-4
Caption: Air pollutants form the condensation nuclei for ice clouds or cirrus clouds (here: Cirrus spissatus). When ammonia, nitric acid and sulfuric acid are present together, they form such condensation nuclei particularly effectively. Credit: Joachim Curtius, Goethe-University Frankfurt
Professor Joachim Curtius
Institute for Atmospheric and Environmental Sciences
Goethe University, Frankfurt, Germany
Phone +49 (0)69 798-40258
A sociological study at Goethe University Frankfurt examines the attitudes of migrants in Europe
The police – your friend and helper? For people immigrating into Europe from another country, this is not always the case. A study at Goethe University shows how the relationship to state power develops among different immigrant groups.
FRANKFURT. The murder of African-American George Floyd in May 2020 led to worldwide protests against police violence. Not least because of these developments, in Europe, too, the relationship between the police and ethnic minorities has been a hotly debated topic in the recent past.
A study by Christian Czymara of Goethe University Frankfurt and Jeﬀrey Mitchell of Umeå University (Sweden), which has just been published, also focuses on the trust placed in the police by immigrants in Europe. The two social scientists have analysed the data of almost 20,000 immigrants from 22 European countries in the period from 2006 to 2019. These data, which originate from the European Social Survey, show that trust in the police is indeed on average higher among immigrants than among the native population. However, the longer people live in the destination country, the more trust tends to erode.
The European Social Survey asks interviewees about their trust in various institutions, which they rank on a scale of 0 to 10. Over half the interviewees originally come from other European countries, 12 percent from Africa, 25 percent from Asia.
The authors have two explanations for the fact that trust decreases with the length of stay: first, the memory of the country of origin, and of the situation there, fades. The contrast between the country of origin and the country of destination is particularly significant for people who have immigrated from countries with a lower level of rule of law to a country that is very advanced in that respect. The second explanation is that these people often experience discrimination in their new surroundings, especially those belonging to an ethnic minority there. This is indicated by the fact that the effect of people's experiences of discrimination is stronger for those who have been in the destination country for longer than for those who have recently arrived. Moreover, comparisons between European countries clearly demonstrate that trust is on average lower where there are more police – for example, in Cyprus, Croatia and Greece. The authors conclude that the size of a police force alone can hardly boost trust in the police, but instead experiences of discrimination must be reduced. Accordingly, efforts in this area would help to maintain the high level of trust in the police among new immigrants and to restore the trust of those who have lived in their host country for a long time.
Publication: Czymara & Mitchell (2022). All Cops are Trusted? How Context and Time Shape Immigrants' Trust in the Police in Europe. Ethnic and Racial Studies. https://www.tandfonline.com/doi/full/10.1080/01419870.2022.2060711
Dr Christian Czymara
Institute of Sociology
Goethe University Frankfurt
Tel.: +49 69 798 36708
First direct visual evidence – ring-like structure like M87* - Theoretical Physicists of Goethe University Frankfurt instrumental in interpreting the data
Astronomers have unveiled the first image of the supermassive black hole at the centre of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the centre of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes. Theoretical Physicists from Goethe University Frankfurt were instrumental in interpreting the data.
FRANKFURT. The image is a long-anticipated look at the massive object that sits at the very centre of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the centre of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced "sadge-ay-star") — is a black hole, and today's image provides the first direct visual evidence of it.
Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a tell-tale signature: a dark central region (called a “shadow") surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.
“We were stunned by how well the size of the ring agreed with predictions from Einstein's
theory of general relativity," says EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “These unprecedented observations have greatly improved our understanding of what happens at the very centre of our galaxy and offer new insights on how these giant black holes interact with their surroundings."
Because the black hole is about 27,000 light-years away from Earth, it appears to us to have about the same size in the sky as a donut on the Moon. To image it, the team created the powerful EHT, which linked together eight existing radio observatories across the planet to form a single “Earth-sized" virtual telescope . The EHT observed Sgr A* on multiple nights, collecting data for many hours in a row, similar to using a long exposure time on a camera.
The enormous amount of observational data collected had to be interpreted theoretically. For this, a research team led by theoretical astrophysicist Luciano Rezzolla from Goethe University Frankfurt used supercomputers to simulate how a black hole could look like when observed by the EHT – based on what had already been known about Sgr A*. In this way, the scientists created a library of millions of images. Then, they compared this image library with the thousands of different images of the EHT to deduce the properties of Sgr A*.
The breakthrough follows the EHT Collaboration's 2019 release of the first image of a black hole, called M87*, at the centre of the more distant Messier 87 galaxy.
The two black holes look remarkably similar, even though our galaxy's black hole is more than a thousand times smaller and less massive than M87* . “We have two completely different types of galaxies and two very different black hole masses, but close to the edge of these black holes they look amazingly similar," says Sera Markoff, Vice Chair of the EHT Science Council and a professor of theoretical astrophysics at the University of Amsterdam, the Netherlands. “This tells us that general relativity governs these objects up close, and any differences we see further away must be due to differences in the material that surrounds the black holes."
This achievement was considerably more difficult than for M87*, even though Sgr A* is much closer to us. EHT scientist Chi-kwan ('CK') Chan, from Steward Observatory, the Department of Astronomy and the Data Science Institute at the University of Arizona, US, explains: “The gas in the vicinity of the black holes moves at the same speed — nearly as fast as light — around both Sgr A* and M87*. But where gas takes days to weeks to orbit the larger M87*, in the much smaller Sgr A* it completes an orbit in mere minutes. This means the brightness and pattern of the gas around Sgr A* was changing rapidly as the EHT Collaboration was observing it — a bit like trying to take a clear picture of a puppy quickly chasing its tail."
The researchers had to develop sophisticated new tools that accounted for the gas movement around Sgr A*. While M87* was an easier, steadier target, with nearly all images looking the same, that was not the case for Sgr A*. The image of the Sgr A* black hole is an average of the different images the team extracted, finally revealing the giant lurking at the centre of our galaxy for the first time.
The effort was made possible through the ingenuity of more than 300 researchers from 80 institutes around the world that together make up the EHT Collaboration. In addition to developing complex tools to overcome the challenges of imaging Sgr A*, the team worked rigorously for five years, using supercomputers to combine and analyse their data, all while compiling an unprecedented library of simulated black holes to compare with the observations.
Luciano Rezzolla, professor of Theoretical Astrophysics at Goethe University Frankfurt, explains: “The mass and distance of the object were known very precisely before our observations. We thus used these tight constraints on the size of the shadow to rule out other compact objects – such as boson stars or wormholes – and conclude that: 'What we're seeing definitely looks like a black hole!'"
Using advanced numerical codes, theorists in Frankfurt have performed extensive calculations on the properties of the plasma accreting onto the black hole. Rezzolla: “We managed to calculate three million synthetic images varying the accretion and radiation emission models, and considering the variations seen by observers at different inclinations with respect to the black hole."
This last operation was necessary because the image of a black hole can be radically different when seen by observers at different inclinations. “Indeed, a reason why our images of Sgr A* and M87* are rather similar is because we're seeing the two black holes from an almost identical angle," Rezzolla explains.
“To understand how the EHT has produced an image of Sgr A* one can think of producing a picture of a mountain peak based on a time-lapse video. While most of the time the peak will be visible in the time-lapse video, there are times when it is not because it is obscured by clouds. On average, however, the peak is clearly there. Something similar is true also for Sgr A*, whose observations lead to thousands of images which have been collected in four classes and then averaged according to their properties. The end result is a clear first image of the black hole at the centre of the Milky Way." Rezzolla concludes.
Scientists are particularly excited to finally have images of two black holes of very different sizes, which offers the opportunity to understand how they compare and contrast. They have also begun to use the new data to test theories and models of how gas behaves around supermassive black holes. This process is not yet fully understood but is thought to play a key role in shaping the formation and evolution of galaxies.
“Now we can study the differences between these two supermassive black holes to gain valuable new clues about how this important process works," says EHT scientist Keiichi Asada from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei. “We have images for two black holes — one at the large end and one at the small end of supermassive black holes in the Universe — so we can go a lot further in testing how gravity behaves in these extreme environments than ever before."
Progress on the EHT continues: a major observation campaign in March 2022 included more telescopes than ever before. The ongoing expansion of the EHT network and significant technological upgrades will allow scientists to share even more impressive images as well as videos of black holes in the near future.
To Goethe University are associated a number of scientists in the EHT Collaboration. Together with Professor Luciano Rezzolla, Dr Alejandro Cruz Orsorio, Dr Prashant Kocherlakota and Kotaro Moriyama, also Prof Mariafelicia De Laurentis (University of Naples), Dr Christian Fromm (University of Würzburg), Prof Roman Gold (University of Southern Denmark), Dr Antonios Nathanail (University of Athens), and Dr Ziri Younsi (University College London) have provided essential contributions to the theoretical research in the EHT Collaboration.
This work has been supported by the European Research Council.
 The individual telescopes involved in
the EHT in April 2017, when the observations were conducted, were: the Atacama
Large Millimeter/submillimeter Array (ALMA), the Atacama Pathfinder Experiment
(APEX), the IRAM 30-meter Telescope, the James Clerk Maxwell Telescope (JCMT),
the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array
(SMA), the UArizona Submillimeter Telescope (SMT), the South Pole Telescope
(SPT). Since then, the EHT has added the Greenland Telescope (GLT), the NOrthern
Extended Millimeter Array (NOEMA) and the UArizona 12-meter Telescope on Kitt
Peak to its network.
ALMA is a partnership of the European Southern Observatory (ESO; Europe, representing its member states), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan, together with the National Research Council (Canada), the Ministry of Science and Technology (MOST; Taiwan), Academia Sinica Institute of Astronomy and Astrophysics (ASIAA; Taiwan) and Korea Astronomy and Space Science Institute (KASI; Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, the Associated Universities, Inc./National Radio Astronomy Observatory (AUI/NRAO) and the National Astronomical Observatory of Japan (NAOJ). APEX, a collaboration between the Max Planck Institute for Radio Astronomy (Germany), the Onsala Space Observatory (Sweden) and ESO, is operated by ESO. The 30-meter telescope is operated by IRAM (the IRAM partner organizations are MPG (Germany), CNRS (France) and IGN (Spain)). The JCMT is operated by the East Asian Observatory on behalf of the Center for Astronomical Mega-Science of the Chinese Academy of Sciences, NAOJ, ASIAA, KASI, the National Astronomical Research Institute of Thailand and organizations in the United Kingdom and Canada. The LMT is operated by INAOE and UMass, the SMA is operated by Center for Astrophysics | Harvard & Smithsonian and ASIAA, and the UArizona SMT is operated by the University of Arizona. The SPT is operated by the University of Chicago with specialized EHT instrumentation provided by the University of Arizona.
The Greenland Telescope (GLT) is operated by ASIAA and the Smithsonian Astrophysical Observatory (SAO). The GLT is part of the ALMA-Taiwan project, and is supported in part by the Academia Sinica (AS) and MOST. NOEMA is operated by IRAM and the UArizona 12-meter telescope at Kitt Peak is operated by the University of Arizona.
 Black holes are the only objects we know of where mass scales with size. A black hole a thousand times smaller than another is also a thousand times less massive.
First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way: 10.3847/2041-8213/ac6674 and https://iopscience.iop.org/article/10.3847/2041-8213/ac6674
All 10 publications in Astrophysical Journal Letters:
First image of the black hole at the centre of the Milky Way
This is the first image of Sagittarius A* (Sgr A*), the supermassive black hole at the centre of our galaxy, captured by the Event Horizon Telescope (EHT). It is the first direct visual evidence of the presence of this black hole. The telescope is named after the “event horizon", the boundary of the black hole beyond which no light can escape.
Although we cannot see the event horizon itself, because it cannot emit light, glowing gas orbiting around the black hole reveals a tell-tale signature: a dark central region (called a “shadow") surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun. The image of the Sgr A* black hole is an average of the different images the EHT Collaboration has extracted from its 2017 observations.
Image credit: EHT Collaboration
Simulation of the Accretion Disk around the Black Hole Sgr A*
Example of a simulation of how the gas orbits the black hole in the center of our Milky Way and emits radio waves at 1.3 mm. Credit: Younsi, Fromm, Mizuno & Rezzolla (University College London, Goethe University Frankfurt)
Making of the image of the black hole at the centre of the Milky Way (image)
The Event Horizon Telescope (EHT) Collaboration has created a single image (top frame) of the supermassive black hole at the centre of our galaxy, called Sagittarius A* (or Sgr A* for short), by combining images extracted from the EHT observations. The main image was produced by averaging together thousands of images created using different computational methods — all of which accurately fit the EHT data. This averaged image retains features more commonly seen in the varied images and suppresses features that appear infrequently.
The images can also be clustered into four groups based on similar features. An averaged, representative image for each of the four clusters is shown in the bottom row. Three of the clusters show a ring structure, but with differently distributed brightness around the ring. The fourth cluster contains images that also fit the data but do not appear ring-like.
The bar graphs show the relative number of images belonging to each cluster. Thousands of images fell into each of the first three clusters, while the fourth and smallest cluster contains only hundreds of images. The heights of the bars indicate the relative “weights", or contributions, of each cluster to the averaged image at top.
Image credit: EHT Collaboration
Luciano Rezzolla, Professor für Theoretische Astrophysik, Goethe-Universität Frankfurt. Credit: Juergen Lecher for Goethe University Frankfurt
Find further animations on how the picture of the black hole in the center of our galaxy was made on the Goethe
University's playlist „Black Hole“
pictures and video clips provided by EHT Collaboration:
When Mongolian gazelles gather on green pastureland, 100,000 animals can soon come together. Then they scatter to the four winds. Why that is and how these animals can be protected in light of Mongolia's booming economy explains animal ecologist Thomas Müller in the current edition of “Forschung Frankfurt", which has now been published in English translation. Under the title “In motion", Goethe University Science Magazine presents a multifaceted spectrum of research projects, viewpoints and analyses by Goethe University researchers.
FRANKFURT. About a million gazelles still inhabit one of the last intact grasslands in the temperate zone: the Eastern Mongolian steppe. When the lush green grass begins to sprout, huge groups of animals gather to graze – and then disappear again into the landscape's vast expanses. Professor Thomas Müller, Senckenberg Biodiversity and Climate Research Centre and Goethe University, and his team have studied the animals' seemingly chaotic migratory behaviour, which is unique worldwide, for many years. Time is pressing, as economic development in Mongolia is on collision course with these wild animals: roads, railway lines and oil production facilities are forcing their way deeper and deeper into the steppe. New nature conservation concepts need to be developed here, as even the large protection zones created by Mongolia in the past years do not meet the animals' need for space: Müller estimates that a gazelle can explore an area the size of Hungary during its lifetime.
In other articles in the current issue of “Forschung Frankfurt", scientists from Goethe University report on their research projects related to various aspects of motion, for example how they teach computers to recognise different movements such as “cutting" or “waving", how ADHD can affect adults too or how two movements in quantum physics are superimposed, each of which only occurs with a certain probability. Other articles explore, for example, how smartphones, which are almost ubiquitous, are changing film as a medium or how sports clubs can foster the integration of immigrants.
Journalists can order the current English-language issue of Forschung Frankfurt (2/2021) free of charge from: firstname.lastname@example.org