Ara h 1 is no minor player. It makes up 12 to 16 percent of total peanut protein and is recognized by IgE antibodies in 70 to 90 percent of peanut-allergic patients. Of the 19 peanut allergens officially designated by the WHO/IUIS Allergen Nomenclature Sub-Committee, Ara h 1 stands out as a seed storage protein whose three-dimensional shape underpins much of its allergenicity. The research team, led by Yong-Qiang Wang and Ying-Chao Li of Changzhou Vocational Institute of Engineering together with colleagues at Jiangyin People’s Hospital, Yangzhou University and Jiangnan University, set out to test whether high-temperature and high-pressure (HTHP) treatment, essentially the saturated steam conditions of commercial autoclaving and retorting, could reshape that protein enough to blunt its immunoreactivity.

The researchers worked with two systems side by side: purified Ara h 1 and a crude peanut protein extract, so they could compare how the allergen behaves in isolation versus within the complex matrix of a real food. They subjected both to steam treatment at 121 degrees Celsius under 0.1 megapascals of pressure and at 135 degrees Celsius under 0.22 megapascals, for durations ranging from 10 to 60 minutes. These temperatures were chosen deliberately because they correspond to standard commercial sterilization protocols, meaning any findings could translate directly into existing food industry practice rather than requiring novel equipment or processing steps.

The results were striking. After 20 minutes at 135 degrees Celsius, the immunoreactivity of purified Ara h 1 fell to 33.4 percent of the untreated control, and after 60 minutes it dropped to just 16.7 percent. In the crude peanut extract, the effect was even more pronounced: immunoreactivity fell to 25.0 percent and 10.0 percent of control levels after 20 and 60 minutes respectively. The team measured this using competitive ELISA with rabbit polyclonal antibodies raised against the allergen, and confirmed the pattern with Western blotting, which revealed that the intact 65-kilodalton Ara h 1 band progressively disappeared while immunoreactive fragments accumulated at roughly 55, 35, 25 and 15 kilodaltons depending on the treatment and the sample matrix.

Electrophoresis told a story of molecular demolition. Under the harshest conditions, 135 degrees Celsius for 20 minutes or longer, small proteins of 15 kilodaltons or less came to dominate the soluble fraction, constituting approximately 56 to 75 percent of total soluble protein after an hour. Soluble protein content of purified Ara h 1 dropped by about 36 percent after 20 minutes at 135 degrees Celsius before plateauing, suggesting that part of the protein had aggregated into insoluble forms or degraded while the remainder resisted further precipitation. Intriguingly, Ara h 1 appeared less thermally stable within the crude extract than on its own, with the intact 65-kilodalton band vanishing more readily in the mixed protein environment, possibly because interactions with a protein of around 55 kilodaltons promoted its aggregation or altered its degradation pathway.

To see what the treatment actually did to the protein’s architecture, the team turned to atomic force microscopy, circular dichroism spectroscopy and intrinsic fluorescence. Native Ara h 1 appeared under the microscope as uniform spheres roughly 5 nanometers tall. After 20 minutes at 135 degrees Celsius, those spheres had transformed into irregular short rod-like aggregates about 3 nanometers in height, and after an hour at either temperature the protein formed heterogeneous globular fragments only around 2 nanometers tall. The morphology mirrored that of Ara h 1 extracted from roasted peanuts in earlier studies, reinforcing the picture of a protein that refolds into compact, fragmented structures after thermal assault.

The spectroscopic data filled in the molecular details. Circular dichroism in the far-ultraviolet region showed that the native protein, initially composed of 20.9 percent alpha-helix, 24.5 percent beta-sheet, 19.4 percent beta-turn and 36.8 percent random coil, progressively lost beta-sheet and beta-turn content while gaining alpha-helical and disordered structures. Near-ultraviolet circular dichroism, which probes the microenvironments of aromatic amino acids, revealed that ordered tertiary structure containing tyrosine residues was nearly eliminated during the first 10 to 20 minutes of treatment, although longer treatment partially restored the tyrosine packing signal. Intrinsic fluorescence showed a slight red shift in the tryptophan emission maximum after treatments longer than 20 minutes, indicating that buried tryptophan residues were increasingly exposed to the aqueous solvent.

These structural changes matter because they plausibly explain the loss of immunoreactivity. Conformational epitopes, the folded three-dimensional shapes that B lymphocytes and IgE antibodies primarily recognize, depend on higher-order protein structure, so dismantling that structure destroys the shapes antibodies bind. Increased exposure of aromatic residues may also make the protein more vulnerable to digestive enzymes such as gastric protease, which cleave preferentially at aromatic amino acids, potentially reducing the allergen’s ability to survive the gut intact and sensitize the immune system. The rise in random coil and alpha-helix content coupled with reduced beta-sheet structure has previously been associated with diminished allergenic reactivity in other food proteins.

The authors are careful to flag important caveats. Immunoreactivity here was assessed with rabbit IgG as a surrogate, not with human IgE from peanut-allergic patients, so the findings demonstrate structural epitope destruction but do not directly measure clinical allergenicity; residual IgE binding in sensitized individuals could still trigger reactions. The analyses were also restricted to the soluble fraction, leaving the insoluble precipitate, which may retain allergenic potential, uncharacterized. Only two temperatures were tested, and questions about long-term stability, flavor, texture and nutrient content remain open before industrial application. The team recommends follow-up work with human serum-based assays, basophil activation tests, and in vivo models to confirm clinical relevance.

Even with those caveats, the implications are compelling. HTHP processing is already an established sterilization technique, so a food manufacturer could in principle reduce the immunoreactivity of peanut ingredients using equipment and protocols that exist today, without genetic engineering, enzymatic additives or chemical treatments that raise consumer safety concerns. As a step toward hypoallergenic peanut products, the study offers a detailed structure-activity account of exactly how heat and pressure dismantle one of the world’s most consequential food allergens, molecule by molecule, and a roadmap for the clinical validation that must come next.

Subject of Research: Structural modification and immunoreactivity reduction of the peanut allergen Ara h 1 by high-temperature and high-pressure processing

Article Title: Structural modifications and immunoreactivity reduction of peanut allergen Ara h 1 under high-temperature and high-pressure processing

Article References: Wang, Y.-Q., Li, Y.-C., Duan, H.-Y., Zhu, H.-K., Jiang, L., & Qian, H. (2026). Structural modifications and immunoreactivity reduction of peanut allergen Ara h 1 under high-temperature and high-pressure processing. Discover Chemistry, 3(1), Article 542. https://doi.org/10.1007/s44371-026-01004-w

Image Credits: AI Generated

DOI: 10.1007/s44371-026-01004-w

Keywords: peanut allergy, Ara h 1, food allergen, high-pressure processing, immunoreactivity, protein structure, circular dichroism, atomic force microscopy, ELISA, food processing, allergenicity, food safety

The research, led by Eddie Guillermo Sanchez-Rueda and colleagues at the Laboratory of Biomolecular Engineering and Bionanotechnology of the Institute of Chemistry at the National Autonomous University of Mexico, focused on two well-characterized antimicrobial peptides with very different origins. The first, aurein 1.2, is a short amphipathic peptide originally described from the skin secretions of Australian tree frogs, known for disrupting bacterial membranes. The second, myxinidin, is a peptide derived from a fish pathogen, which has attracted attention for its activity against a broad range of Gram-negative bacteria. Both peptides are small, positively charged, and membrane-active, which makes them attractive drug candidates but also makes them difficult guests in a living production cell.

The team’s central design decision was to genetically fuse each peptide to a triblock polypeptide the authors call CSB, a protein-engineering scaffold that self-assembles into nanoparticles. Rather than letting the antimicrobial peptides float freely in the yeast cell, where their membrane-disrupting activity could poison the host and depress yields, the fusion strategy tethers them to a larger, structured carrier. Once the fusion proteins are produced and purified, the CSB block drives the molecules to organize themselves into discrete protein nanoparticles, effectively immobilizing the peptides within a supramolecular architecture. This kind of self-assembling carrier serves a dual purpose: it shields the producing organism during fermentation, and it creates a nanoparticle format that could later be useful for delivery or formulation of the antimicrobial cargo.

Producing the fusion proteins in Pichia pastoris required careful optimization of the fermentation conditions, and this is where much of the study’s practical value lies. Pichia is a workhorse of industrial biotechnology, prized for its ability to grow to very high cell densities and for a strong, tightly regulated promoter that responds to methanol. The researchers systematically varied the concentrations of glycerol, used as a carbon source for building biomass, and methanol, used to induce expression of the recombinant genes, along with the pH of the culture medium. The outcome of these experiments was strikingly clear: the single most important factor was allowing the yeast to accumulate extensive biomass before the methanol induction was triggered, combined with letting the medium acidify to a permissive pH of approximately 3.

Under those optimized conditions, the gains were dramatic. The aurein 1.2–CSB fusion, abbreviated Aur-CSB, increased in yield by up to 35.3-fold, reaching 35.95 plus or minus 19.05 milligrams per liter of culture. The myxinidin–CSB fusion, Myx-CSB, showed a more modest but still substantial improvement of up to 5.5-fold, reaching 12.96 plus or minus 5.75 milligrams per liter. The difference between the two constructs is itself informative, because it illustrates a familiar reality of recombinant protein production: even two peptides of similar size and function can behave very differently once fused to the same carrier, and yields must be tuned construct by construct rather than assumed from a general protocol.

After purification, the critical question was whether the fusion proteins actually did what the design intended: assemble into nanoparticles. The researchers turned to two complementary biophysical techniques to find out. Atomic force microscopy, which scans a sharp probe across a surface to map its topography with nanometer resolution, and dynamic light scattering, which infers particle size from fluctuations in scattered laser light, both confirmed self-assembly. Interestingly, the three constructs adopted different morphologies. The bare CSB polypeptide formed rod-shaped nanoparticles with an average height of 3.55 plus or minus 0.38 nanometers, while both the Aur-CSB and Myx-CSB fusions formed globular particles, with average heights of 9.79 plus or minus 1.56 nanometers and 9.28 plus or minus 0.99 nanometers respectively. The attached antimicrobial peptides thus appear to influence not just the yield but the geometry of the assembled structures.

With the nanoparticles in hand, the team moved to a preliminary test of biological function, using Escherichia coli as the target organism. Rather than relying on a single assay, they combined fluorescent probes that report on different aspects of bacterial health. A live/dead viability test based on SYTO 9 and propidium iodide staining was used to assess membrane integrity: SYTO 9 stains all cells green, while propidium iodide, which cannot cross intact membranes, only enters and stains red those cells whose membranes have been compromised. Hoechst dye was used to stain bacterial DNA, providing an additional readout. Both the culture supernatants containing the expressed AMP-CSB fusions and the purified nanoparticles displayed preserved antimicrobial activity in these assays, indicating that the peptides had not lost their membrane-disrupting potency by being locked into the nanoparticle format.

The significance of that last point is hard to overstate. One of the recurring fears in fusion-based production of antimicrobial peptides is that burying the active sequence inside a larger protein or a supramolecular structure will neutralize it, forcing researchers to choose between yield and activity. This study suggests the trade-off can be avoided: the CSB scaffold protects the yeast during production, assembles into defined nanoparticles after purification, and still leaves the antimicrobial function intact enough to compromise E. coli membranes. The authors are careful to frame the activity data as preliminary, and fluorescence-based membrane assays are a first screening step rather than a full pharmacological characterization, but the proof of concept is complete across the whole chain from gene to functional nanoparticle.

The broader context makes the work timely. As multidrug-resistant infections continue to spread, the pipeline for new antibiotics remains thin, and antimicrobial peptides are among the few candidate classes moving from academic labs toward clinical and agricultural applications. What has been missing, in many cases, is a manufacturing route that is scalable, economical, and compatible with the biological activity of the product. Yeast fermentation in Pichia pastoris is already used industrially for enzymes, vaccines, and biopharmaceuticals, so demonstrating that AMP-nanoparticle fusions can be produced there, with yields improved by simple and transferable fermentation parameters, lowers a significant barrier. The finding that high pre-induction biomass and acidic culture conditions around pH 3 boost production is the kind of process knowledge that can be directly adopted by other groups working on similar constructs.

There is also a nanotechnology dimension that extends beyond antibiotics. The CSB triblock polypeptide belongs to a growing family of genetically encoded, self-assembling protein building blocks that can form nanoparticles of controlled shape and size without chemical crosslinkers. Fusing functional peptides to such scaffolds turns the nanoparticles into programmable multivalent display platforms, with potential uses in drug delivery, vaccination, biosensing, and materials science. By showing that the identity of the fused peptide changes the assembly morphology, from rods to globules, the Mexican team has added a data point to the emerging design rules for these systems. The study, which was supported by UNAM-PAPIIT funding and carried out within a doctoral program spanning UNAM and the University of Groningen, establishes key parameters for efficient production of self-assembling AMP-based protein nanoparticles in Pichia pastoris and provides a scalable platform for their further development and functional characterization. If subsequent work confirms and extends the antimicrobial findings to other pathogens, the humble yeast tank could become an unexpected factory for the next generation of nanostructured antibiotics.

Subject of Research: Recombinant production of antimicrobial peptide nanoparticles in Pichia pastoris

Article Title: Production of antimicrobial peptides fused to a nanoparticle-forming polypeptide using Pichia pastoris

Article References: Sanchez-Rueda, E. G., Cruz-Garcia, B. B., Hernandez-Cortes, F. O., Trejo-Perez, M. A., Valentinotti-Bonardi, L., Clairin-Savage, A., Ramírez-Carreto, S., & Hernandez-Garcia, A. (2026). Production of antimicrobial peptides fused to a nanoparticle-forming polypeptide using Pichia pastoris. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-026-14033-3

Image Credits: AI Generated

DOI: 10.1007/s00253-026-14033-3

Keywords: antimicrobial peptides, Pichia pastoris, nanoparticles, self-assembly, recombinant protein production, aurein 1.2, myxinidin, antibiotic resistance, biotechnology, fermentation optimization, atomic force microscopy, E. coli