The study is the first to evaluate microalgal fertiliser on malting barley at field scale, and the first to ask whether algae-grown grain still makes acceptable malt. Barley is the fourth most cultivated cereal in the world, and in the United Kingdom it is second only to wheat in production, contributing £1.16 billion to the economy. Roughly a quarter of UK barley goes to brewing and distilling, a premium market that adds £5.5 billion through Scotch Whisky alone. Crucially, distilleries and breweries produce enormous volumes of nutrient-rich wastewater that must be treated by law before release. Species of Chlorella have already been shown to thrive on such waste, stripping out nitrogen and phosphorus with removal efficiencies above 90 and 80 percent respectively in most studies. The researchers envision a circular economy in which algae clean distillery wastewater, accumulate the nutrients, and are then returned to the fields as fertiliser, closing the barley-to-malt-to-whisky loop.

To test the concept rigorously, the team ran three glasshouse trials and one field trial using spring barley cv. Laureate, currently the dominant malting variety in Scotland. In the glasshouse, they compared four treatments: an unfertilised negative control, dried Chlorella vulgaris powder alone, the same powder supplemented with potassium, calcium and other nutrients that the algae supplied in lower amounts, and a mineral salt positive control modelled on Hoagland solution ratios. Nitrogen was normalised across the fertilised treatments so that total available nitrogen reached 118 kilograms per hectare, the recommended rate for malting barley set by the Agriculture and Horticulture Development Board. The trials used three different soils from fields near Dundee, each with distinct pH and carbon-to-nitrogen ratios, to ensure the findings were robust to soil-to-soil variation rather than artefacts of a single growing medium.

The results were striking in their consistency. Across all three glasshouse experiments, plants grown with microalgal fertiliser showed no statistically significant difference from mineral-fertilised plants in any measured trait: not in earless dry biomass, tiller number, filled grain count, thousand grain weight, or grain dimensions. All three fertilised treatments significantly outperformed the unfertilised control, with earless dry biomass increasing by 18 to 28 percent, tillers by 11 to 28 percent, and total filled grain by 13 to 21 percent. The only transient differences appeared in the speed of early development, where algae-fed plants briefly tillered or elongated faster than some counterparts, but these gaps vanished by later growth stages and had no bearing on final yield. The team used linear mixed models treating experiment and block as random effects, and found no significant treatment-by-experiment interactions, meaning the fertiliser source behaved the same way regardless of soil or season.

Concerns that algae might release nitrogen too slowly and starve young plants, a worry raised in earlier literature, were not borne out. During early tillering, there were no significant differences in leaf length, leaf area, aboveground biomass or the Normalised Difference Vegetation Index, a spectral measure of leaf greenness and photosynthetic capacity, between any of the treatments. This aligns with prior work showing that phosphorus from algal biomass is readily accessible to wheat for up to six weeks after sowing. The slow-release character of algal nitrogen and phosphorus, with plant-available nitrogen reported at around 31 percent after 95 days in previous studies, may even be an advantage, since lower concentrations of soluble nutrients reduce runoff and the eutrophication that follows it.

The field trial, sown at Balruddery Farm in Angus in April 2024, took the test into conditions closer to those faced by real farmers. Here the team used Chlorella pellets and 24–4–14 NPK granules, both delivering an additional 61.6 kilograms of nitrogen per hectare to bring the soil up to the 118-kilogram target, arranged in a 3 by 3 Latin square design with nine plots per treatment. Emergence exceeded 99 percent in every plot. At harvest, dry grain yield was statistically indistinguishable between algae and mineral fertiliser plots, and both outyielded the unfertilised control by 42 and 59 percent respectively. Thousand grain weight, a key quality metric, was likewise equal between the two fertilised treatments and significantly higher than the control. Intriguingly, algae-fed plants produced slightly more grains per ear and longer ears than mineral-fertilised plants, though these differences did not translate into a yield advantage.

The most novel and commercially sensitive part of the study came after harvest, when grain from each plot was malted in quadruplicate and analysed at Chivas Brothers’ Glen Keith Technical Centre. Malt quality determines whether barley can enter the premium brewing and distilling markets, and the team measured fine hot water extract strength, soluble nitrogen, total malt nitrogen and predicted spirit yield, the industry’s estimate of how much alcohol a tonne of malt will produce. On every one of these indicators except total malt nitrogen, malt from algae-grown barley was statistically indistinguishable from malt grown with mineral fertiliser. Both fertilised treatments produced malt with significantly higher extract strength and predicted spirit yield than the unfertilised control. The single difference, total malt nitrogen, actually favoured the algae treatment in one respect: algae-grown malt had lower nitrogen than mineral-grown malt, sitting as a significant intermediate between the control and mineral treatments.

That lower nitrogen could prove a commercial bonus. The malting industry typically prefers grain nitrogen at the lower end of its target range, particularly for malt whisky distilling, and all values in this study fell below the typical industry maximum of 1.60 percent. If microalgal fertiliser consistently delivers lower grain and malt nitrogen while maintaining yield and extract quality, distillers seeking low-nitrogen malt may find it especially attractive. The researchers caution, however, that the malt in this experiment was under-modified, meaning the sugars and proteins of the endosperm were not fully mobilised during germination, likely due to poor germination conditions rather than insufficient malting time. The comparisons between treatments remain valid, but confirmation in properly modified malt from further field trials is still needed.

The authors are equally candid about the hurdles that remain. Microalgae cultivated solely for fertiliser are not yet economically competitive with mineral products, but coupling algal cultivation to wastewater treatment, turning a costly waste stream into a saleable co-product, could change the calculus. For wastewater-grown algae, safety testing would be essential to ensure that heavy metals, pharmaceuticals or other contaminants are not accumulated to harmful levels, a requirement already applied to other organic fertilisers in Scotland. Nutrient mineralisation from organic sources is also temperature-dependent, which could make availability unpredictable across a growing season, and surface-applied algal pellets may struggle to incorporate into soil if applied late as a top dressing. The researchers suggest a hybrid approach, ploughing in most of the algal nutrient load at sowing and supplementing with a smaller, later mineral application, though this retains some dependence on synthetic fertiliser.

Even with those caveats, the study represents a genuine proof of concept: at equal nitrogen rates, in three soils and one field season, barley fed on Chlorella vulgaris matched mineral fertiliser on yield and nearly every malt quality measure the industry cares about. The work extends earlier findings on wheat, which had terminated before crop maturity, into full-cycle cereal production and, for the first time, into the malting pipeline itself. The next steps, the authors say, are multi-year trials across different soils and climates, investigations of the molecular mechanisms and genotypic variation underlying the response, and experiments using algae grown specifically on distillery wastewater. If those succeed, the nutrients that distilleries currently pay to discard could one day flow back into the barley fields, making a dram of whisky a little greener from the ground up.

Subject of Research: Using microalgal biomass as a fertiliser to sustain barley yield and malt quality compared with mineral fertiliser

Article Title: Barley can utilise algal fertiliser to maintain yield and selected malt quality indicators compared to mineral fertiliser

Article References: Ashworth, D. J., Masson, S., Mulholland, T., Bulgarelli, D., & Houston, K. (2026). Barley can utilise algal fertiliser to maintain yield and selected malt quality indicators compared to mineral fertiliser. Plant and Soil. https://doi.org/10.1007/s11104-026-09049-7

Image Credits: AI Generated

DOI: 10.1007/s11104-026-09049-7

Keywords: barley, microalgae, Chlorella vulgaris, fertiliser, malt quality, sustainable agriculture, circular economy, nitrogen, Haber-Bosch, whisky, soil, crop yield

Electrochemical ammonia synthesis promises a way out of this bind. In principle, a modular electrolyser powered by renewable electricity could split water for protons and electrons, draw nitrogen straight from the air, and combine the two into ammonia at ambient temperature and pressure, wherever cheap clean power happens to be available. In practice, the field has been haunted by a stubborn problem: energy efficiency. Among the various electrochemical strategies explored over the past decade, one approach has clearly outperformed the rest. It relies on lithium, which under the right conditions can bind and activate the nitrogen molecule, an extraordinarily stable species whose triple bond resists almost every attempt at chemical persuasion at room temperature. This lithium-mediated nitrogen reduction can indeed deliver ammonia at practical rates, but its underlying chemistry imposes what researchers believed was an intrinsic ceiling on how efficient the process could ever become.

That ceiling has now been broken. A team at Monash University in Melbourne, working with colleagues at RMIT University, has demonstrated that the key lies not in tweaking the electrolyte or the operating conditions, but in redesigning the cathode itself. Writing in Cell Press Blue, the researchers describe a new class of lithium-alloying electrode materials that allow the lithium-mediated reaction to proceed at substantially more favourable electrical potentials while still activating nitrogen and producing ammonia. The work, led by Dr Rebecca Hodgetts of the Monash University School of Chemistry, provides proof of concept that a limitation long treated as fundamental to the technology can be engineered away through electrode design.

To appreciate why this matters, it helps to understand how lithium-mediated nitrogen reduction works. In the conventional configuration, a current passed through the electrolytic cell deposits metallic lithium on the cathode. This freshly formed lithium reacts spontaneously with dissolved nitrogen gas, forming lithium nitride, which is then protonated to yield ammonia and regenerate lithium, closing the catalytic cycle. The problem is thermodynamic. Depositing lithium metal requires a large electrical potential, and once that energy has been sunk into making the metal, a significant fraction of it is unavoidably lost as heat rather than being carried into the nitrogen-fixation step. The result is a voltage penalty baked into the chemistry itself, one that no amount of optimisation of catalysts, electrolytes or current densities could remove. Energy efficiencies reported for the lithium-mediated route have therefore remained stubbornly low, far below the thresholds proposed for commercially viable green ammonia.

The Monash team’s insight was to sidestep the formation of free lithium metal altogether. Instead of a conventional electrode on which lithium plates out as a solid metal, the researchers employed gallium-based materials that alloy with lithium. When current flows, lithium atoms insert into the gallium-containing host, forming a lithium alloy rather than a layer of pure metal. Crucially, this alloyed lithium remains chemically potent enough to react with nitrogen and sustain the ammonia-producing cycle, but the electrical potential at which the alloying reaction occurs is markedly more favourable than the potential needed to deposit metallic lithium. In effect, the electrode material absorbs part of the thermodynamic burden, changing the energy landscape of the entire reaction sequence. As Dr Hodgetts put it, the new cathode materials change the rules of the game by redefining this fundamental limit and opening previously unexplored opportunities for more energy- and cost-effective production of green ammonia.

The experimental results are striking. Under optimised conditions, the team achieved ammonia production with a faradaic efficiency of 96 plus or minus 6 per cent, meaning that almost every electron pushed through the cell went into making ammonia rather than into wasteful side reactions such as hydrogen evolution. Faradaic efficiency has long been a sore point in electrochemical nitrogen fixation, where competing hydrogen production can devour the majority of the current, particularly in aqueous systems. A figure approaching unity in a lithium-mediated system indicates that the alloying cathode not only lowers the operating potential but also preserves the selectivity that makes this chemistry attractive in the first place. The researchers further estimate that the findings could support future electrochemical ammonia production with an overall energy efficiency of at least 22 per cent, a level that begins to approach the territory discussed in commercial feasibility assessments.

The team is careful to note that further improvements are still required to reach the proposed commercial targets for green ammonia electrolysers. A 22 per cent estimated energy efficiency, while transformative relative to the intrinsic limit of the conventional lithium-metal route, does not by itself guarantee economic competitiveness with fossil-derived ammonia, whose prices are heavily distorted by decades of scale and subsidised feedstocks. What the study does establish, and what its significance rests on, is that the longstanding energy barrier is not an immutable fact of nature. It is a consequence of a particular electrode chemistry, and electrode chemistry can be changed. That reframing converts a perceived dead end into an open design space, which is precisely the kind of shift that has historically accelerated energy technologies from laboratory curiosities to industrial processes.

Emeritus Professor Douglas MacFarlane, also of the Monash School of Chemistry and one of the leading figures in electrochemical nitrogen reduction, emphasised that the discovery widens the chemical toolkit available to the entire field. According to Professor MacFarlane, the field has essentially been limited to a single cathode process based on lithium-mediated nitrogen reduction, and introducing lithium-alloying materials broadens that chemistry considerably. Instead of being constrained to one composition, researchers can now begin exploring different combinations of materials capable of activating the extremely unreactive nitrogen molecule under relatively mild conditions. Gallium is unlikely to be the last word; the alloying strategy invites systematic exploration of other low-melting or soft metals and mixed-composition hosts, each potentially offering a different balance of potential, stability, nitrogen reactivity and cost.

Considerable engineering challenges remain between the present results and a working industrial electrolyser. Lithium-mediated systems typically operate in non-aqueous electrolytes with carefully controlled proton donors, and scaling such cells from laboratory electrodes to large-area, long-lived cathodes is a nontrivial undertaking. Gallium-based materials bring their own questions of mechanical stability, cost and behaviour over thousands of hours of cycling. Professor Alexandr Simonov, also from the School of Chemistry, identified the immediate priority as translating the discovery from laboratory experiments into practical devices. The next key step, he said, is to integrate the new lithium-alloying cathodes into electrolyser prototypes that more closely mimic the conditions needed for practical ammonia production, while also scaling up the cathodes and demonstrating long-term ammonia production at competitive energy efficiency, a milestone he described as critical to taking the technology towards commercial application.

If those steps succeed, the implications extend well beyond a single reaction. Decentralised ammonia production powered by stranded renewable resources, wind farms in remote regions or solar installations far from any grid connection, could decouple fertiliser supply from natural gas markets and reduce the vulnerability of global food systems to energy price shocks. Ammonia produced this way could likewise serve as a storable, transportable form of renewable energy, feeding into the emerging infrastructure for carbon-free shipping fuels. The Monash technology is being further developed through ongoing research in collaboration with Jupiter Ionics Pty Ltd, a Monash University spin-out company, signalling that the team intends to pursue the path from proof of concept to product. For a chemical industry that has produced ammonia the same way for more than a century, the demonstration that a supposedly fundamental efficiency limit can be redesigned out of existence is a genuinely consequential result, and one that other laboratories working on renewable nitrogen fixation will now be racing to build upon.

Subject of Research: Lithium-alloying cathode design for energy-efficient electrochemical reduction of nitrogen to green ammonia

Article Title: New electrode design breaks key barrier to greener ammonia production

Article References: New electrode design breaks key barrier to greener ammonia production. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: green ammonia, electrochemistry, lithium-mediated nitrogen reduction, cathode design, lithium alloys, gallium, faradaic efficiency, renewable energy, fertilisers, Haber-Bosch, Monash University, energy efficiency

The reaction in question, known as electrocatalytic nitrate reduction to ammonia, or NO3RR, has been attracting intense research attention in recent years. The concept is elegantly simple: apply an electric current to a catalyst immersed in nitrate-containing water, and the nitrate ions are progressively reduced, ultimately yielding ammonia that can be harvested from the electrolyte. Because the process can run on electricity from solar panels or wind turbines, it offers a route to ammonia synthesis that is decoupled from fossil fuels. Even better, the feedstock is a pollutant that society currently pays to remove. The challenge lies in the chemistry. Nitrate is a remarkably stable molecule, and converting it to ammonia requires a sequence of eight electron transfers and multiple protonation steps. If the reaction takes a wrong turn along the way, it can stall at nitrite, which is itself toxic, or end as nitrogen gas, which wastes the nitrogen entirely. Controlling that pathway is the central problem the review addresses.

The authors, researchers from Guizhou University in China and the Bioeconomy Science Institute in New Zealand, focus their analysis on cobalt-based electrocatalysts, a family of materials they argue offers an unusually compelling combination of performance and practicality. Corresponding author Professor Hu Li explains that cobalt stands out among candidate metals because it is abundant and inexpensive compared with precious metal alternatives, while possessing a unique electronic structure that strongly adsorbs nitrate ions. According to Li, the sp3 orbitals of cobalt atoms can form stable bonds with nitrate, which facilitates the initial and often rate-limiting reduction step that strips an oxygen atom from the nitrate molecule. That initial activation is where many catalysts falter, so a metal that grips nitrate tightly has an inherent advantage in driving the reaction forward.

The performance numbers reported for some cobalt-based systems are striking. Li notes that certain cobalt catalysts have achieved close to 100 percent Faradaic efficiency, a measure of how much of the electrical current flowing through the cell is directed into producing ammonia rather than into side reactions. The chief competitor for electrons is the hydrogen evolution reaction, in which water is split into hydrogen gas instead of ammonia being formed. In dilute nitrate solutions especially, hydrogen evolution can dominate and render the process uneconomical. A catalyst that channels nearly all the current into ammonia therefore represents a major step toward practical devices. Faradaic efficiency alone is not enough, however; the review emphasizes that ammonia production rate, current density, stability over long operating periods, and the energy cost per kilogram of ammonia all matter when evaluating whether a laboratory result can scale to industrial relevance.

Because the reaction pathway involves so many intermediates, the selectivity of the catalyst depends on how strongly each of those transient species binds to its surface. The review describes how researchers can fine-tune these binding energies through deliberate structural design. Alloying cobalt with other metals shifts the electronic environment of the active sites, introducing defects creates undercoordinated atoms that bind intermediates differently, and engineering the crystal structure changes which crystal facets are exposed to the electrolyte. By adjusting these variables, Li says, the binding of intermediates can be steered so that the reaction follows the eight-electron route to ammonia with high selectivity rather than diverting to nitrite or nitrogen gas. This principle of intermediate-binding control, borrowed in part from the broader field of electrocatalysis, is the conceptual thread that runs through the material families surveyed in the review.

Among the material classes examined are monometallic cobalt, cobalt alloys, oxides, sulfides, phosphides, and metal-organic frameworks, along with derivatives formed from those precursors during operation. The review highlights several standout examples that illustrate what careful design can achieve. Cobalt-nickel alloys have delivered industrial-level current densities while maintaining 100 percent Faradaic efficiency in neutral media, a combination that matters because real nitrate waste streams are typically neither strongly acidic nor strongly alkaline. Phosphorus-doped cobalt catalysts have achieved ultra-high ammonia production rates exceeding 200 milligrams per hour per square centimeter of catalyst, placing them among the most productive nitrate reduction systems reported. High-entropy alloys containing cobalt, in which multiple metal elements share a single disordered lattice in ordered atomic arrangements, have been shown to suppress the competing hydrogen evolution reaction, simultaneously boosting both activity and stability.

Each of these material families brings its own trade-offs. Oxides and sulfides tend to be easy to synthesize and robust, but their surfaces may restructure under the reducing potentials required for nitrate conversion, sometimes creating new active phases and sometimes degrading. Phosphides and phosphorus-doped materials benefit from the electronic modulation that phosphorus imparts, enhancing nitrate adsorption and hydrogenation kinetics. Metal-organic frameworks offer extraordinarily high surface areas and precisely tunable metal centers, but their electrical conductivity and long-term durability under operating conditions remain hurdles. The review’s comparative treatment of these classes gives researchers a map of the design space, showing which strategies have demonstrably improved selectivity, which have improved throughput, and which remain promising but unproven at scale.

Beyond the catalysts themselves, the review surveys methodological advances that are accelerating the field. Machine learning is increasingly being used for high-throughput catalyst screening, allowing computational models to predict which compositions and structures are most likely to bind nitrate and its intermediates with the right strength before any material is synthesized in the laboratory. In-situ and operando characterization techniques, which probe the catalyst while it is actually working, are revealing how surfaces evolve during the reaction, exposing dynamic changes such as surface reconstruction, oxidation state shifts, and intermediate adsorption that static ex-situ measurements miss entirely. These tools are shifting the field from trial-and-error discovery toward rational design, and they are helping to explain why certain cobalt configurations outperform others rather than simply documenting that they do.

The authors also look past the catalyst to the reactor and the process. They envision integrated systems that combine nitrate reduction with ammonia separation, so that the ammonia formed in the electrolyte is continuously extracted rather than accumulating and potentially being re-oxidized or lost. Coupling the electrochemical cell with upstream nitrate concentration steps and downstream product recovery will be essential if the technology is to treat real wastewater economically. Durability remains a central concern: catalysts that perform brilliantly for hours in the laboratory must survive months or years in industrial service, resisting corrosion, poisoning, and structural degradation. Li frames the review as a roadmap for developing next-generation cobalt-based electrocatalysts that can turn a global pollutant into a valuable resource, and suggests that with continued progress on catalyst durability and system engineering, nitrate-to-ammonia conversion could become a cornerstone of sustainable chemistry and the circular economy.

The broader significance of this line of research is hard to overstate. If electrocatalytic nitrate reduction matures into a commercial technology, it would simultaneously address water pollution, reduce dependence on the fossil-fuel-intensive Haber-Bosch process, and create a distributed source of ammonia that could be sited wherever nitrate waste and renewable electricity coexist. Farms, wastewater treatment plants, and industrial facilities could become ammonia producers rather than nitrogen polluters, closing the loop on a nutrient cycle that industrial civilization has so far run in one direction. Cobalt, abundant and affordable, may prove to be the metal that makes that vision practical. The review makes clear that the fundamental chemistry is increasingly well understood; what remains is the engineering discipline of turning high-performing laboratory catalysts into durable, economical, large-scale systems.

Subject of Research: Cobalt-based electrocatalysts for electrochemical nitrate reduction to ammonia

Article Title: Recent progress on cobalt-based electrocatalysts for nitrate reduction to ammonia

Article References: Recent progress on cobalt-based electrocatalysts for nitrate reduction to ammonia. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ammonia synthesis, nitrate reduction, electrocatalysis, cobalt catalysts, Haber-Bosch, water pollution, renewable energy, Faradaic efficiency, high-entropy alloys, metal-organic frameworks, machine learning, circular economy

Nitrogen fixation is the conversion of atmospheric nitrogen gas, which makes up roughly 78 percent of the air we breathe, into ammonia that living cells can incorporate into amino acids, nucleotides and other essential molecules. The obstacle is the nitrogen-nitrogen triple bond, one of the strongest chemical bonds known in nature, which locks the two atoms together with an energy that neither plants nor animals can unlock. Only certain microorganisms, equipped with the enzyme nitrogenase, can break it under the mild conditions of ambient pressure and temperature that life tolerates. Industrial chemistry, by contrast, needs the Haber-Bosch process, with its high temperatures, high pressures and substantial energy consumption, to accomplish the same transformation at scale.

The nitrogenase enzyme carries at its heart the most complicated metallocofactor known in biology, a cluster of metal and sulfur atoms that orchestrates the reduction of N2 to ammonia. Nitrogenases come in three main varieties, distinguished by the metal at the centre of the cofactor: molybdenum, vanadium or iron alone. The molybdenum form is the best studied and generally the most efficient, yet how the different metal centres enable the breaking of the triple bond, and how the three enzyme families relate to one another evolutionarily, remain open questions in biochemistry.

Methanocaldococcus infernus offered an unusual opportunity to probe those questions. The archaeon thrives in marine volcanic areas, and the team led by Tristan Wagner managed to cultivate it in the laboratory under conditions that forced it to fix nitrogen at temperatures above 90 degrees Celsius. How, Wagner wondered, could an enzyme tasked with splitting the N2 triple bond remain functional in heat that denatures most proteins within seconds? The answer, it turns out, lies in a molecular architecture of remarkable robustness.

When the researchers isolated the nitrogenase directly from the microbe, they found that the protein does not begin to fall apart until around 90 degrees Celsius, and a fraction of it even survives at 98 degrees, just shy of water’s boiling point. Nevena Maslać, the study’s first author, compared the fate of ordinary proteins in such conditions to egg white cooked in hot water, noting that this enzyme is instead built for exactly those extremes. Intriguingly, the enzyme is not active at room temperature; it produces ammonia only when hot. That thermal rigidity proved to be a scientific gift, because it stabilised reaction states that normally collapse before they can be studied.

Obtaining a detailed picture of the enzyme demanded a tour de force spanning microbial physiology, native enzyme purification, biochemistry and structural biology, all conducted under strictly oxygen-free conditions. Nitrogenase metallocofactors are exquisitely sensitive to oxygen, which irreversibly damages them, so every step of the work had to exclude air. The team crystallised the enzyme and examined the crystals at the Institut de Biologie Structurale in Grenoble, using the on-site synchrotron, a circular particle accelerator that generates intense X-rays capable of resolving atomic-scale structure.

The resulting images delivered a near-atomic-resolution view of the simplest nitrogenase known to date, and one with a strikingly hybrid character. The archaeal enzyme combines structural features of all three nitrogenase families, the molybdenum, vanadium and iron-only forms. This mosaic architecture supports the idea that ancestral nitrogenases, the ancient systems from which the modern families evolved, may have resembled this archaeal enzyme more closely than their bacterial counterparts. In other words, studying M. infernus’s nitrogenase may be the closest researchers can get to examining a molecular fossil of the original nitrogen-fixing machinery.

Confirming that the enzyme truly carried a molybdenum cofactor pushed the synchrotron instrumentation to its absolute limits, according to Wagner. The measurement succeeded, detecting the characteristic molybdenum signal, but it also delivered an unexpected bonus. The team observed a so-called turnover state of the enzyme, a configuration believed to represent an intermediate step in the nitrogen reduction reaction, that had previously been captured only in vanadium and iron-only nitrogenases. Seeing this state in a molybdenum-containing enzyme for the first time stunned the researchers, and it carries a significant implication: nitrogenases of all three metal types may universally follow the same mechanistic pattern when they dismantle the N2 triple bond.

The significance of understanding nitrogen fixation extends well beyond deep-sea microbiology. Nitrogen-fixing microorganisms such as M. infernus do more than make ammonia; they are also major players in Earth’s carbon cycle, generating roughly half of the methane present in the atmosphere. Wagner and colleagues point to a future in which such heat-loving organisms, or the enzymes they carry, could serve as biological platforms for converting gases into useful products, including methane and ammonia, powered by green hydrogen as an energy source. Enzymes that operate at near-boiling temperatures could offer advantages of reaction speed and stability that their mesophilic cousins cannot match.

Agriculture stands to gain as well. Wagner speculates about a future in which crops might one day obtain nitrogen directly from atmospheric N2, freeing farming from its heavy dependence on industrial fertilisers. Today’s fertiliser production through the Haber-Bosch process consumes substantial energy and is associated with greenhouse gas emissions, while the overuse of fertilisers drives eutrophication of waterways and other environmental damage. For now, however, the study delivers something more fundamental: an updated molecular view of one of biology’s most remarkable chemical reactions, seen through an enzyme that keeps working at temperatures where almost everything else in the cell falls apart.

Subject of Research: Structure and mechanism of a hyperthermophilic archaeal nitrogenase involved in biological nitrogen fixation

Article Title: Molecular insight into biological nitrogen fixation close to the boiling point

Article References: Molecular insight into biological nitrogen fixation close to the boiling point. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: nitrogenase, nitrogen fixation, Methanocaldococcus infernus, deep-sea hydrothermal vents, metallocofactor, molybdenum, hyperthermophile, structural biology, synchrotron, ammonia, Haber-Bosch, Nature Communications

The significance of the work lies in what it replaces. Virtually all industrial fermentation that yields nitrogen-rich products, from amino acids to nucleotides, depends on ammonium salts or urea as the nitrogen feedstock, and those inputs trace back to Haber–Bosch ammonia synthesis. That process, which combines atmospheric nitrogen with hydrogen under extreme pressures and temperatures, consumes an estimated one to two percent of global energy output and generates substantial carbon dioxide emissions as a byproduct of hydrogen production from natural gas. Biological nitrogen fixation, carried out by the nitrogenase enzyme complex in certain bacteria and archaea, performs the same chemical transformation at ambient temperature and pressure using ATP and electrons, offering a potentially far gentler route to usable nitrogen.

Azotobacter vinelandii has long served as the model organism for aerobic nitrogen fixation, a biologically awkward combination since oxygen both damages nitrogenase and competes for the electrons the enzyme needs. The bacterium survives this paradox through extraordinarily high respiratory rates that consume oxygen before it can reach the enzyme. Previous efforts had engineered A. vinelandii to excrete ammonium, the natural next step after nitrogen fixation, since the fixed nitrogen normally feeds the cell’s own biosynthesis. But the researchers behind the new study found that studies on actually using that excreted ammonium as a nitrogen source for other microbes remained limited, and that ammonium production levels were too low to be industrially interesting.

To push yields higher, the team took aim at NifA, the transcriptional activator that switches on the entire nif regulon encoding the nitrogen fixation machinery. They constructed A. vinelandii strains by integrating a nifA overexpression cassette, driven by the strong tac promoter, into the algU locus of the chromosome. This chromosomal integration strategy matters for stability: rather than relying on a plasmid that could be lost during cultivation, the engineered construct is inherited by every daughter cell, ensuring the nitrogen fixation program stays dialed up throughout a fermentation run. The resulting strain stably produced ammonium at a concentration of 1 gram per liter in simple flask cultures, a level the researchers describe as a solid baseline for the platform.

Flask cultures, however, are a proving ground rather than a production environment. The team then scaled the process into a jar fermenter, where they could control oxygen transfer, pH and feeding with far greater precision. By combining fed-batch cultivation, in which fresh carbon source is supplied incrementally to avoid depletion or overflow metabolism, with antifoam treatment to keep the aerated broth from foaming over and lactic acid addition to manage the culture’s chemistry, they raised ammonium production to 1.5 grams per liter. Each of these process interventions addresses a practical bottleneck: fed-batch keeps the energy supply matched to the nitrogenase’s enormous ATP appetite, antifoam protects oxygen transfer and prevents contamination pathways, and acid addition stabilizes the pH as ammonium accumulates and shifts the broth’s acid-base balance.

With a reliable ammonium source in hand, the researchers turned to the second half of the partnership. Corynebacterium glutamicum is arguably the most successful amino acid production organism in industrial biotechnology, responsible for the bulk of the world’s several-million-ton annual L-glutamate output, the flavor-enhancing component of monosodium glutamate. In the co-culture scheme, the engineered A. vinelandii functions as a living nitrogen fertilizer, continuously fixing atmospheric nitrogen gas and releasing ammonium into the shared medium, while C. glutamicum assimilates that ammonium and channels it through its existing metabolic machinery into L-glutamate. The division of labor elegantly sidesteps the need to purify or concentrate the intermediate: the product of one microbe is the substrate of the other, delivered in situ.

The results demonstrated the concept convincingly. Co-cultivation of the ammonium-producing A. vinelandii strain with C. glutamicum enabled the production of 2 grams per liter of L-glutamate from nitrogen gas. While that titer remains well below the tens of grams per liter achieved in conventional glutamate fermentations fed with commercial ammonium, the demonstration establishes a complete biological pipeline from atmospheric dinitrogen to a finished amino acid in a single vessel. The researchers frame the strategy as a contribution to the development of environment-friendly fermentation processes for producing various nitrogen-containing compounds from nitrogen gas, suggesting the platform could extend well beyond glutamate to other amino acids, nucleotides and nitrogenous chemicals.

The engineering choices embedded in the study reveal a careful reading of nitrogenase regulation. NifA sits atop a hierarchy of control mechanisms that bacteria use to avoid wasting energy on nitrogen fixation when fixed nitrogen is already available, a regulatory logic that normally shuts the system down precisely when engineers want it running. By overexpressing NifA from a constitutive tac promoter, the team effectively overrides the ammonium-sensing feedback that would otherwise silence the nif genes as product accumulates. Placing the cassette at the algU locus, which governs stress responses in A. vinelandii, reflects a deliberate choice of a neutral genomic landing site that disrupts native function minimally while granting stable, high-level expression of the activator.

Scaling challenges remain before such co-cultures could challenge conventional plants. Nitrogenase is an enzyme of notorious fragility and metabolic cost, demanding roughly sixteen ATP per molecule of nitrogen reduced, and maintaining two microbial populations with different physiological optima in one fermenter requires balancing oxygen availability, carbon source preference and growth rates. The fed-batch jar fermenter results, with their combination of antifoam and lactic acid management, hint at the kind of process engineering refinement that will determine whether titers can climb toward commercial relevance. The involvement of Kikkoman Corporation, a company with deep roots in fermentation technology, alongside academic groups at The University of Tokyo’s Department of Biotechnology and Collaborative Research Institute for Innovative Microbiology, suggests industrial interest in closing that gap. Several of the authors have filed patent applications on the work, underscoring its perceived commercial potential.

For now, the study stands as a proof of concept with a compelling narrative: a flavor compound that seasons much of the world’s food, assembled in part from the air itself, by two bacteria cooperating in a fermenter. If the platform’s titers can be improved through further strain and process optimization, nitrogen-fixing co-cultures could offer fermentation industries a route to decouple amino acid production from synthetic fertilizer inputs, trimming both energy demand and carbon emissions. The researchers position their work as a step toward fermentation processes that draw their nitrogen directly from the atmosphere, converting a century-old industrial dependency into a biological partnership.

Subject of Research: L-glutamate production from nitrogen gas via co-culture of engineered Azotobacter vinelandii and Corynebacterium glutamicum

Article Title: L-Glutamate production from nitrogen gas by co-culturing Corynebacterium glutamicum with Azotobacter vinelandii

Article References: Ito, Y., Yoshidome, D., Araki, Y., Ito, K., Hidaka, M., Kosono, S., & Nishiyama, M. (2026). L-Glutamate production from nitrogen gas by co-culturing Corynebacterium glutamicum with Azotobacter vinelandii. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14031-5

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14031-5

Keywords: Azotobacter vinelandii, Corynebacterium glutamicum, nitrogen fixation, L-glutamate, co-culture, nifA overexpression, ammonium production, Haber-Bosch, metabolic engineering, fed-batch fermentation, nitrogenase, sustainable biotechnology