Physically programmed vegan leather emulating the mechanical and sensory characteristics of animal leather from once-discarded gluten

Abstract

The production of animal-derived leather raises substantial environmental and ethical concerns, prompting the search for sustainable alternatives. However, most synthetic leathers are not biodegradable and fail to replicate the tactile and mechanical properties of natural hide, while bio-based films often exhibit poor toughness/elongation and hydration sensitivity. Here, we report a chemical toughener-free process that transforms wheat gluten—a widely available but underutilized plant protein—into durable and biodegradable vegan leather. The facile process combines heating and UV exposure to induce depth-gradient protein denaturation of only plant-based ingredients. In the first stage, thermal conditioning promotes uniform distribution of glutenin and gliadin and optimizes hydrogen bonding, enhancing structural integrity. Subsequent brief, high-intensity heating and UV treatment initiate thiol-mediated crosslinking among cysteine residues and oxidized amino acids, forming a molecular network. The resulting material exhibits an exceptionally high toughness of 4.7 MJ m⁻³ and comparable water resistance to animal leather. The protein-based structure replicates the frictional feel, pliability, and surface micro-texture of natural leather, providing a comparable aesthetic and tactile experience. This material is fully soil-degradable, has a reduced carbon footprint by up to 13-fold compared to animal leather, provides waterless dyeing, and is even edible by insects. Therefore, the vegan leather developed in this study offers a scalable and eco-friendly alternative to conventional leather.

---

New concepts

Gluten, widely recognized only as a component in bread making, has been underestimated as a functional biomaterial. Its intrinsic ability to form a three-dimensional disulfide-bonded network imparts both elasticity and durability—features uniquely observed in gluten, unlike any other plant-based protein. In this study, we exploited this distinctive property to fabricate an eco-friendly alternative leather. By applying solely physical treatments such as heat and UV irradiation, the hydrophobicity and water resistance of gluten films were significantly enhanced. This work represents the first attempt to utilize native gluten protein to mimic the mechanical performance and tactile characteristics of natural leather. Whereas previous studies relied on strong alkalis like NaOH to solubilize gluten, we instead directly compounded gluten powder with water and glycerol, followed by hot-pressing to form a cohesive film. Subsequent surface exposure to heat and UV induced the formation of covalent crosslinks such as cysteinyl-DOPA and dityrosine, which further reinforced the structure and enhanced water repellency—thus yielding “gluten leather.” This approach is meaningful as it demonstrates a simple, solvent-free, and environmentally sustainable route to transform a bio-derived protein into a high-performance material with the look and feel of leather. It highlights the untapped potential of gluten as a renewable structural biopolymer beyond its conventional role in food applications.

Introduction

Natural leather, renowned for its unique texture and durability, has been a staple of fashion, furniture, and furnishings for centuries. Approximately 1.67 × 109 m² of leather is produced worldwide annually, with the global trade value reaching US $70 billion per year.¹ However, the production of natural leather raises significant ethical concerns regarding animal welfare and has considerable environmental impacts. The livestock sector, which supplies leather rawhide, contributes about 14.5% of global greenhouse gas emissions.² Annually, 3.5 million tons of chemicals are used in the leather manufacturing process, and waste from the tanning process alone is known to contaminate over 55 000 hectares of land (Fig. 1a).^1,3

Fig. 1 (a) Necessity of vegan leather and properties of wheat gluten. (b) Gluten-based vegan leather making process and formation of gluten network structure.

The abovementioned issues have spurred interest in alternatives, such as synthetic leather, with ongoing research focused on developing sustainable leather substitutes. The most widely used synthetic leather materials, poly(vinyl chloride) (PVC) and polyurethane (PU), are petroleum-based and come with significant environmental and functional drawbacks.⁴ Unlike natural leathers, synthetic leathers are non-biodegradable and toxic, with PVC production and incineration generating 4.9 kgCO₂-eq per kg of global warming potential (GWP) and releasing hazardous dioxins and hydrogen chloride.⁵ Synthetic leathers, being hydrophobic and lacking moisture-wicking ability and a natural surface texture, fail to replicate the unique tactile and viscoelastic properties of biologically derived natural leather. These differences significantly affect consumer perceptions and limit their application in certain high-performance luxury markets.

Given these challenges, plant-derived leather alternatives have emerged as promising sustainable solutions and are broadly categorized as carbohydrate- and protein-based materials. Carbohydrate-based materials utilize fibrillar polysaccharides such as cellulose. Notable examples include Desserto® and Piñatex®, derived from cactus and pineapple leaf fibers, which are agricultural waste products. These materials offer advantages such as enhanced biodegradability and a reduced carbon footprint. However, their predominant carbohydrate composition leads to inherent limitations in replicating the complex viscoelastic behavior of natural leather; in particular, carbohydrate-based materials have low stretchability and durability under wet conditions.⁶

In contrast, protein-based leather alternatives, although less extensively explored, have attracted growing interest because of their compositional similarity to natural leather.⁴⁵ Natural leather is a protein-based material primarily composed of collagen fibers that form a complex interwoven matrix.⁷ Their diverse secondary and tertiary structures provide excellent toughness, flexibility, and stretchability. Some plant proteins, such as soybean protein isolates, have been used to develop free-standing films.⁸ However, these systems still face challenges in achieving sufficient mechanical robustness without relying on synthetic polymers or chemical crosslinkers.⁹

Wheat gluten (WG), a protein complex derived from wheat, has unique viscoelastic properties that closely resemble those of natural leather. Gluten is widely recognized as the key component responsible for the extensibility and structural integrity of wheat flour dough. It enables remarkable elasticity under high strain, allowing the dough to resist rupture while maintaining its shape. Gluten primarily consists of two protein fractions: glutenin and gliadin.¹⁰ Glutenin, with its high molecular weight 30 000–90 000, forms a stable β-sheet-rich, spiral-like network through disulfide bonding of abundant cysteine residues, imparting strength and elasticity to the structure. In contrast, gliadin, which is composed largely of random coils, contributes to flexibility and extensibility by interacting with glutenin via disulfide linkages, particularly in aqueous environments.

In parallel, demand for gluten-containing food products has declined, and the gluten-free market surged from $4.63 billion in 2017 to $6.47 billion by 2023, resulting in an increasing surplus of wheat gluten as a byproduct of flour production.¹¹ This surplus provides an abundant, low-cost, and renewable resource, positioning wheat gluten as a raw material for biocomposites.

However, research on gluten-based biocomposites has predominantly focused on food packaging applications.^12,44 These film materials lack the toughness required to replace leather and exhibit poor water resistance. While the addition of chemical crosslinkers and water-repellent coatings can address these shortcomings, these methods compromise gluten's intrinsic advantages, including biodegradability and biorenewability.¹³ This prompted efforts to overcome these limitations through physical modification of the protein structure. As a promising solution, physical protein denaturation methods, including heat and UV treatments, have demonstrated the ability to promote intermolecular hydrogen bonding, hydrophobic interactions, and covalent cross-linking without the need for chemical additives.¹⁷

In this study, we developed a biodegradable protein-based material using plant-derived wheat gluten and glycerol as natural plasticizers, without the use of any chemical cross-linkers or synthetic additives. The film demonstrated leather-like strength, reaching 70% of that of natural leather and matching synthetic alternatives, while outperforming most reported substitutes (Fig. 2c). Furthermore, heat and UV treatments were applied to induce protein denaturation and additional cross-linking, which enhanced water resistance and contributed to a more realistic leather-like texture and performance. Approximately 2% of gluten's amino acid residues are cysteine, which are converted to cystine by the formation of disulfide bonds during oxidation. This transformation reinforces the protein's secondary and tertiary structures through physical denaturation, enabling the reorganization of glutenin and gliadin into a cohesive protein network. This network imparts mechanical toughness, elasticity, and shape adaptability, which are critical for leather-like behavior. In addition, oxidative crosslinking involving aromatic amino acids, such as tyrosine, tryptophan, and histidine, further reinforces the protein matrix. In particular, the oxidation of tyrosine can generate reactive intermediates, such as dihydroxyphenylalanine (DOPA) and DOPA-quinone, facilitating additional covalent bonding pathways.³² The final material is fully soil degradable, significantly reduces the carbon footprint, and provides a scalable and environmentally friendly alternative to conventional animal or synthetic leathers.

Fig. 2 (a) WG-vegan leather wallet, scale bar = 1 cm. (b) 100% elongation of WG-vegan leather by UTM. (c) Ashby's plot of different types of leather (Table S2). (d) Water contact angle, swelling ratio, friction coefficient, shore A hardness, and heart loop test of various leathers (Fig. S2).

Results and discussion

Fabrication of WG-based vegan leathers

WG-based vegan leathers were fabricated by blending gluten, glycerol, and water in a 2 : 0.3 : 1 weight ratio to form a cohesive viscoelastic dough. This mixture was molded into films through mild thermal processing (∼60 °C), partially denaturing the protein structure to enable cohesive film formation. The resulting ∼1.5 mm thick beige film served as a base for further surface modification via high heat and UV treatment to enhance water resistance while retaining interior flexibility. The entire leather-making process involves four elemental crafting techniques: (i) planetary mixing, (ii) hot pressing, (iii) UV irradiation, and (iv) additional surface heat treatment. The following sample nomenclature was adopted: the untreated wheat gluten powder is referred to as ‘WG-powder’, and the hydrated dough prepared via step (i) is denoted as ‘WG-dough’. The film fabricated using heat and pressure (i + ii) was labelled ‘WG-film’. When this film is further treated by UV irradiation (i + ii + iii), it is termed ‘WG-UV film’, while exposure to surface heat treatment results in ‘WG-heat film’ (i + ii + iv). The fully treated sample, having undergone all four steps (i + ii + iii + iv), is designated as ‘WG-leather’. The detailed experimental procedures are provided in the SI (Experimental Section).

Leather-like physical performance and texture

The elongation at break of conventional plant-based films ranges from 15 to 48%, which limits their use as alternatives to natural leather.^21–23 Moreover, previous gluten-based films were mostly produced using the solvent casting method, resulting in low tensile strengths ranging from 0.4 to 1.75 MPa.^24,25 This limits their applications to those requiring minimal mechanical strength, such as food packaging. To evaluate their mechanical performance, the tensile strength and elongation at break of the gluten films were measured using a universal tensile testing machine (UTM) (Fig. 2c and Table S2). Among the specimens, natural leather exhibited the highest average tensile strength, ranging from 15 to 19 MPa, and an elongation of 55–62%. The synthetic PU leather exhibited a tensile strength of 5–12 MPa and an elongation range of 57–67%. However, alternative leathers demonstrated tensile properties that resulted in toughness values approximately 50–80% lower than those of natural animal leather. In comparison, the developed WG-leather demonstrated a tensile strength of 10–14 MPa and elongation at break of 60–70%, resulting in a toughness of 4.6 MJ m⁻³, surpassing synthetic leather in energy absorption capability. Furthermore, by adjusting the relative proportions of glycerol, which contributes to rigidity and ductility, the mechanical properties of the WG-vegan leather could be tuned. This tunability enables the fabrication of either highly ductile films with an elongation of up to 180% or rigid films with a tensile strength of 15 MPa, covering a broad application spectrum. Tensile property data under different conditions are provided in the SI (Table S2). Moreover, tannic acid and iron chloride were employed for natural tanning, leading to a notable enhancement of the gluten leather's mechanical properties (17.2 MPa, 44%), comparable to those of natural leather (17.9 MPa, 58%) (Table S2), through the well-known coordination complex formation between polyphenols and metal ions.³⁶

Natural leather exhibits adequate resistance to water swelling while simultaneously absorbing ambient moisture and responding to skin humidity, such as sweat. These properties are inherently difficult to achieve simultaneously. In most synthetic or bio-based alternatives, improving the water repellency tends to reduce the hygroscopic responsiveness, making it challenging to replicate the balanced tactile comfort of natural leather. Among the WG-vegan leather series, the WG-leather exhibited the best leather-like balance. As shown in Fig. 2d and Fig. S2, WG-leather exhibits a contact angle of 65° and a swelling ratio of 70%, which are comparable to those of bovine leather (typically 60–70° contact angle and 55–65% swelling ratio, depending on processing). In contrast, PU-based synthetic leather typically exhibits a much higher contact angle (>85°) and a significantly lower swelling ratio (<40%). These results indicate that after dual heat and UV treatment, WG-leather exhibits dual functionality close to that of natural leather. This performance stems from the denaturation and reconfiguration of the protein matrix under thermal treatment, which improves dimensional stability, and the additional UV exposure, which modifies the surface polarity. It is worth noting that, as reported in the literature, gluten film may still undergo partial swelling in aqueous environments, potentially leading to mechanical softening or weakening under prolonged exposure.^24,25

Natural leather is valued for its unique combination of tactile and mechanical properties, including surface friction, vertical and lateral elasticities, and soft draping properties. These characteristics are difficult to replicate in synthetic alternatives, which often lack both the nuanced texture and viscoelastic recovery behavior of natural leather. To assess the suitability of WG-vegan leather as an alternative, key parameters such as the coefficient of friction against human skin, Shore A hardness, and lateral flexibility (via a heart loop test) were measured. Among the WG-vegan leather series, WG-leather exhibited the most leather-like response across all metrics. As shown in Fig. 2e–g, the WG-leather demonstrated a friction coefficient of 1.1, a Shore A hardness of 75, and a lateral flexibility of 1.75%, which closely matched those of bovine leather (0.9, 80, and 2.5%, respectively). In contrast, the WG film, synthetic leather, and rubber exhibited statistically significant deviations from these benchmarks. The softness, drape, and mechanical responsiveness of the WG leather can be attributed to its protein-based structure. Thermal denaturation induces chain mobility and partial alignment, whereas UV treatment modifies surface polarity and microstructure. This combination facilitates intermolecular interactions and reversible deformation, enabling the material to mimic the viscoelastic behavior of natural leather. Such concurrent expressions of softness and elasticity have rarely been achieved for synthetic polymer films. These results highlight the structural merits of protein-derived materials for the design of high-performance, skin-compatible leather alternatives.

Protein denaturation induced by surface treatment

The observed improvements in the mechanical strength, hydrophobicity, and water resistance of WG-leather can be attributed to cysteine- and oxidizable amino acid–mediated cross-linking, particularly through thiol–disulfide exchange reactions involving cysteine residues induced by thermal and UV treatments.³³ The fabrication of WG-leather involves two distinct external triggers that induce protein denaturation. The first occurs during film formation and additional heating of the film surface, where heat transforms gluten powder into a cohesive protein network.²⁰ The second trigger is UV surface treatment, which further modifies the protein structure. These stimuli induce significant physical changes in protein secondary structures and molecular bonding.³⁹ During the initial mixing stage, hydrated conditions facilitated the homogeneous blending of glutenin and gliadin subunits, aided by glycerol and water.¹⁴ X-ray diffraction (XRD) analysis revealed that this process reduced the intermolecular spacing and aligned the molecular arrangement, thereby enhancing the combined elasticity and ductility of the film (Fig. S5). Furthermore, the formation of an intermolecular three-dimensional hydrogen bonding network, which was reinforced by progressive dehydration, was confirmed by Fourier-transform infrared spectroscopy (FTIR), indicating a more stabilized protein secondary structure by an increase in β-sheets and a decrease in α-helix and β-turn structures (Fig. S6).¹⁸ Through XPS analysis, the surface-treated WG-leather was also found to exhibit decreased C–N (amide) bonding, increased C–C (covalent) bonding, and the formation and oxidation of disulfide bonds (Fig. S10).

In addition, thermal and UV stimuli induced significant chemical modifications, primarily involving thiol groups of cysteine residues. These treatments are known to cleave existing disulfide bonds and promote thiol–disulfide exchange through localized oxidation reactions.⁴² To investigate the cysteine-mediated chemical changes in detail, we analyzed three types of samples: Sample #1 (WG-dough), Sample #2 (WG-film), and Sample #3 (WG-leather).

The oxidation of two cysteine residues into cystine (disulfide) is a known reaction facilitated by atmospheric oxygen during the film-mixing stage.¹⁵ Consequently, disulfide bonds were already present in the gluten network prior to further processing. These disulfide bonds are dynamic in nature and can undergo temporary radical-driven cleavage under thermal or UV stimulation.⁴⁰ This facilitates disulfide exchange reactions and enables the reformation of new cross-links, contributing to the structural stabilization of the protein network.⁴¹ High-performance liquid chromatography (HPLC) dedicated to amino acid analysis was used to quantify the cystine i.e. disulfide and tyrosine contents of each sample. LC–mass spectrometry (LC–MS) and LC–tandem mass spectrometry (LC–MS/MS) were employed to characterize structural changes and potential cross-linking events.³⁴ In the LC–MS and LC–MS/MS analyses, the samples were subjected to 24 h hydrolysis to fully cleave peptide chains. This allowed the selective detection of dipeptides or dimers, which can be interpreted as evidence of newly formed, stable inter- or intramolecular cross-links, most likely resulting from cysteine-mediated reactions because the formation of such structures from native peptide bonds under these conditions is highly improbable (Fig. S7). Additionally, fluorescence intensity changes and surface and cross-sectional SEM images were monitored to track the oxidative coupling of aromatic amino acids, particularly tyrosine, as a supplementary indicator of chemical cross-linking and changes in porosity and toughness.

A comparative analysis of Samples #1 and #2 indicated that chemical modifications of the amino acid residues were induced by mild thermal treatment. The cystine content increased after mild heating, whereas the tyrosine content remained relatively constant (Fig. 3c). This can be attributed to the formation of disulfide bonds under thermal and oxidative conditions, facilitated by the optimal temperature range for disulfide bond formation (60–80 °C), reduced intermolecular distance between cysteine residues due to applied pressure, and decreased water content resulting from evaporation. A comparative analysis of Samples #2 and #3 revealed amino acid modifications induced by UV treatment and subsequent surface heating. Specifically, the cystine content decreased from 3.45% to 1.89% following the intense thermal and UV treatments, suggesting that cystine may have reacted with other functional groups to form new compounds. Similarly, the tyrosine content decreased progressively from 3.57% in the WG film to 2.78% in the WG leather. These findings indicate that tyrosine is actively involved in oxidative crosslinking, primarily through thiol-mediated coupling and subsequent oxidation to 3,4-dihydroxyphenylalanine (DOPA) and quinone derivatives (Fig. 3d).⁴¹ LC–MS and LC–MS/MS analyses confirmed the formation of the covalently crosslinked compound 2-S-cysteinyl-DOPA, resulting from the reaction between cysteine and oxidized tyrosine (DOPA).¹⁹ The formation of 2-S-cysteinyl-DOPA is proposed to proceed via nucleophilic addition of a thiolate ion to a DOPA-derived quinone intermediate, followed by tautomerization.^16,35 In some cases, subsequent cleavage by a second thiolate ion may regenerate free DOPA and cystine (Fig. 3d). The formation of these cross-linked compounds likely contributed to the improved hydrophobicity and water resistance of the WG-leather.

Fig. 3 (a) Blue, green, yellow, red fluorescence microscopy, (b) SEM surface and cross-sectional images, and (c) cystine, tyrosine composition of Sample #1 (WG-dough), Sample #2 (WG-film), and Sample #3 (WG-leather). (d) Possible coupling reactions between cystine and oxidized amino acids during thermal and UV treatment.

Fluorescence microscopy (Fig. 3a) revealed that the presence of reactive amino acid residues facilitated the formation of covalent crosslinks between the oxidative units, including dityrosine, disulfide bonds, and cysteinyl-DOPA linkages. These oxidative couplings between the aromatic groups significantly enhanced the fluorescence properties of the material.⁴³ As the extent of the thermal and UV treatments increased, the overall fluorescence intensity also increased. Notably, the sample subjected to both heat and UV treatment (Sample #3) exhibited strong fluorescence in the 500–600 nm range, with a 3- to 5-fold increase in the green (490–530 nm) and yellow (565–615 nm) channels compared to the untreated control (Sample #1). This enhancement supported the formation of stable aromatic crosslinked structures.

The surface and cross-sectional morphologies of Samples #1, #2, and #3 were analyzed using scanning electron microscopy (SEM) (Fig. 3b). Sample #2 exhibited the roughest surface, whereas Sample #3, which was treated with both heat and UV light, showed noticeably reduced surface roughness. In the cross-sectional view, Sample #1 displays the largest and most abundant pores, whereas Samples #2 and #3 exhibit smaller and fewer pores, respectively. These results suggest that the pressure and thermal treatments enhanced the structural density and stability. Furthermore, optical microscopy (OM) revealed the formation of a distinct surface layer in Sample #3 that was not observed in Sample #2. A detailed analysis of this layer is presented in Fig. S4.

Collectively, these chemical and spectroscopic results demonstrate that thermal and UV surface treatments not only increase intermolecular hydrogen bonding and molecular packing but also promote the formation of robust covalent crosslinking networks. These structural transformations significantly improved the water resistance and durability of the WG leather, underscoring the potential of physical processing to enhance the performance of plant protein-based materials.³⁸

Environmental impacts

Cradle-to-gate environmental impact. A life-cycle assessment (LCA) was conducted under Scenario 1 to evaluate the cradle-to-gate environmental impact of WG-leather (Fig. 4). The analysis encompassed five major stages: gluten extraction, planetary mixing, hot pressing, surface treatment, and oven drying. The global warming potential over a 100-year period (GWP 100) was calculated using Ecoinvent datasets. WG-leather exhibited a GWP 100 of 1.63 kgCO₂-eq., which is approximately 13-fold and 6-fold lower than those of bovine leather and PU-based synthetic leather, respectively. Remarkably, it outperformed mycelium-based leather-consuming nutrients, a material that is often promoted as a sustainable next-generation alternative.²⁶

Fig. 4 (a) Cradle-to-gate LCA of wheat gluten leather, (b) wheat gluten leather making process, (c) soil biodegradability of wheat gluten leather over time, (d) superworm consumption of wheat gluten leather over time, and (e) superworm survival rate and body weight change according to feed type. ((c)–(e) experiments were conducted in triplicate, and the results are presented as mean ± standard deviation).

Furthermore, beyond Scenario 1, additional scenarios were explored to evaluate the potential to reduce the environmental impact further through energy-saving and material-sourcing strategies. Scenario 2 assumes that wheat gluten is derived as a by-product of gluten-free food production, eliminating the need for dedicated extraction and resulting in a reduced GWP 100 of 0.47 kgCO₂-eq.²⁸ Given the rapid growth of the gluten-free market, repurposing residual gluten from food processing is both practical and sustainable.²⁷ Scenario 3 considers the potential for post-use energy recovery through incineration of WG-leather, which could partially offset the energy input required during the drying and thermal processing stages. This scenario achieved an additional reduction of 0.078 kgCO₂-eq per kilogram, lowering the total GWP 100 to 1.55 kgCO₂-eq.²⁸ These findings highlight the substantial environmental advantages of WG-leather over conventional leather alternatives. Moreover, the potential for sourcing raw materials as by-products and the feasibility of post-use energy recovery further enhance the viability of WG-leather as a sustainable alternative.

Notably, retanning and dyeing greatly contribute to the carbon footprint of conventional leather production (1.2 and 0.7 kgCO₂-eq. per 1 kg of leather, respectively).^29,46 We demonstrate that the formation of coordination complexes between tannic acid and iron(II) chloride has the potential to combine dyeing and tanning into a single process.³⁶ By adjusting the ratio of the components, a variety of colors can be achieved while significantly reducing the carbon footprint compared with conventional methods. The different WG-leather colors are shown in Fig. S3.

End-of-Life (EoL) options in view of material recovery. As described above for Scenario 3, even when the energy is recovered through incineration, the benefit in terms of kgCO₂-eq. per 1 kg remains limited, and concerns arise regarding the emission of particulates during combustion.³⁷ Therefore, rather than prioritizing energy recovery, this section explores material recovery by investigating the feasibility of biodegradation through composting and its potential use as animal feed in livestock farming.

First, disintegration under simulated composting conditions was assessed in accordance with the ISO 20200 standard using five different materials, as shown in Fig. 4c: WG-heat film, WG-UV film, WG-leather, polylactic acid (PLA), and poly(butylene adipate-co-terephthalate) (PBAT). Degradation was characterized over a period of seven weeks by measuring the weight loss percentage. All types of WG-vegan leathers exhibited over 90% biodegradation, whereas commercial biodegradable plastics, PLA and PBAT, degraded less than 50%. From an energy recovery perspective, the gluten film undergoes composting, during which its nitrogen is converted into ammonium and subsequently stabilized as nitrate through nitrification, making it a potential source of nitrogen fertilizers.²⁸

The bioconversion potential of WG leather, composed entirely of natural plant-based ingredients, was evaluated using superworms (Zophobas atratus).⁴⁷ Given their high protein content and widespread use as both livestock feed and human food, superworms were chosen as biological vectors for post-consumer feed valorization.³¹ This approach explored the feasibility of transforming WG leather into a sustainable nutrient source at the end-of-life stage.³⁰Fig. 4d and e show the weight loss of various films over time and the corresponding weight change and survival rate of the superworms, respectively. The results indicate that superworms exhibit significant degradation ability towards WG-vegan leathers, as evidenced by their complete degradation (100%), nearly 100% survival rate, and approximately 20% increase in body weight within two weeks. Conversely, PLA and PBAT exhibited much slower and lower degradation rates, with a superworm survival rate of approximately 80%, an approximately 6% increase in body weight, and degradation limited to within 40%. Unlike PLA and PBAT, which lack a nitrogen source, WG contains nitrogen, which enhances the survival rate of mealworms and enables their efficient conversion into a protein source for feed. Additionally, WG-vegan leathers pose minimal toxicity concerns because they are composed entirely of biodegradable raw materials and are manufactured solely through physical treatments without the use of toxic chemicals.

Conclusions

In this study, we developed an additive-free method to convert WG, an abundant protein byproduct, into mechanically robust, water-resistant, and biodegradable vegan leather. Using a two-step spatiotemporal treatment involving thermal denaturation followed by UV surface exposure, we achieved depth-specific protein modifications that emulated the structural and functional qualities of animal leather. Heat treatment enhances the internal structure through disulfide bond formation between glutenin and gliadin, thereby increasing the strength and flexibility of the material. Subsequent UV exposure induces thiol-disulfide exchange and oxidative cross-linking, especially the formation of cysteinyl-DOPA compounds, which densify the surface molecular network of WG-leather. These transformations improve water resistance. The WG-leather exhibited a tensile strength of up to 12 MPa and a toughness of 4.6 MPa, exceeding those of conventional plant- and fungi-based leather alternatives. From an environmental standpoint, WG-leather has a significantly lower carbon footprint than bovine and synthetic leathers, particularly when sourced as a gluten-free byproduct. Its natural biodegradability and compatibility with insect feed pathways support the circular economy. Importantly, all enhancements were achieved through physical treatment alone, without chemical crosslinkers, plasticizers, or coatings. This minimalist approach preserves the intrinsic biodegradability of WG-leather and makes it edible to mealworms, underscoring a new paradigm in sustainable material design that prioritizes simplicity, functionality, and environmental responsibility. Furthermore, the fabrication strategy presented here shows strong potential for industrial scalability, as it can be readily implemented using existing manufacturing equipment such as dough mixers, compression molding systems, and roll-to-roll or conveyor-based UV coating lines already established in large-scale production.^48,49

Author contributions

S. K. contributed to the conceptualization, methodology, data curation, validation, and visualization of this work, and took the lead in writing the original draft. J. C. carried out the investigation involving HPLC-based amino acid composition analysis. S. L. contributed to the investigation and data curation for the life cycle assessment calculations. G. S. carried out the investigation related to the superworm-based degradation test. D. S. H. and J. P. supervised the research and contributed to reviewing and editing the manuscript. D. X. O. and J. P. contributed to the conceptualization, resource provision, supervision, and review and editing of the manuscript, and led the funding acquisition and project administration. All authors have read and approved the final version of the manuscript.

Conflicts of interest

There are no conflicts to declare.

Data availability

The datasets supporting this article are available in the supplementary information (SI). Supplementary information is available. See DOI: https://doi.org/10.1039/d5mh01579k.

Additional data are available from the corresponding author upon request.

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (MSIT) (RS-2024-00408795 and 2022R1C1C1004660), the Technology Innovation Program (RS-2024-00488505) funded by the Ministry of Trade, Industry, and Energy (MOTIE, Korea), and the Korea Ministry of Oceans and Fisheries (RS-2025-02305544).

References

1. S. Dixit, A. Yadav, P. D. Dwivedi and M. Das, J. Cleaner Prod., 2015, 87, 39–49,  DOI:10.1016/j.jclepro.2014.10.017.
2. Food and Agriculture Organization of the United Nations (FAO), Livestock solutions for climate change, 2017.
3. M. Jones, A. Gandia, S. John and A. Bismarck, Nat. Sustainable, 2021, 4, 9–16,  DOI:10.1038/s41893-020-00606-1.
4. S. B. Park, H. Kwak, D. Lee, G. Shin, M. Jang, H. Jung, H. Jeon, H. J. Kim, J. Park and D. X. Oh, Adv. Mater., 2025, 37, 2417266,  DOI:10.1002/adma.202417266.
5. M. H. Kudzin, Materials, 2023, 17, 173,  DOI:10.3390/ma17010173.
6. G. Y. Kefale, J. Eng., 2023, 2023, 1629174,  DOI:10.1155/2023/1629174.
7. L. G. Hole and R. E. Whittaker, J. Mater. Sci., 1971, 6, 1–15,  DOI:10.1007/BF00550284.
8. S. Kang, Q. Bai, Y. Qin, Q. Liang, Y. Hu, S. Li and G. Luan, Food Res. Int., 2024, 196, 115042,  DOI:10.1016/j.foodres.2024.115042.
9. C. U. Lee, S. J. Kim, R. B. Dietrich, A. L. Girard and A. J. Boydston, Green Chem., 2024, 26, 9814–9822,  10.1039/D4GC02932A.
10. H. Wieser, Food Microbiol., 2007, 24, 115–119,  DOI:10.1016/j.fm.2006.07.004.
11. J. S. Woomer and A. A. Adedeji, Crit. Rev. Food Sci. Nutr., 2021, 61, 14–24,  DOI:10.1111/1750-3841.16454.
12. J. Xu and Y. Li, J. Food Sci., 2023, 88, 582–594,  DOI:10.1111/1750-3841.16454.
13. X. Zhang, J. Wu, H. Chen and R. Zhuo, Polym. Degrad. Stab., 2010, 95, 2309–2317,  DOI:10.1016/j.polymdegradstab.2010.09.001.
14. T. Ogawa and Y. Matsumura, Nat. Commun., 2021, 12, 1708,  DOI:10.1038/s41467-021-22019-0.
15. E. Fuentes-Lemus, Front. Chem., 2022, 10, 956123,  DOI:10.1002/cche.10572.
16. L. Nie, Z. Zhang, L. Li and J. Chen, Mater. Horiz., 2023, 10, 2923–2946,  10.1039/D3MH00516J.
17. Y. Eom, S. M. Kim, M. Lee, H. Jeon, J. Park, E. S. Lee, S. Y. Hwang, J. Park and D. X. Oh, Nat. Commun., 2021, 12, 621,  DOI:10.1038/s41467-021-20931-z.
18. N. Wehrli, C. Grau, A. Rieder, M. G. Schmid and E. J. Windhab, Int. J. Biol. Macromol., 2021, 173, 26–33,  DOI:10.1016/j.ijbiomac.2021.01.008.
19. Z. Zhao, D. Huang, Y. Zhou, X. Han and W. Ding, J. Agric. Food Chem., 2020, 68, 6900–6909,  DOI:10.3390/molecules27010015.
20. P. Koehler, K. L. Wieser and H. Schopf, Eur. Food Res. Technol., 2010, 231, 535–544,  DOI:10.1016/j.jcs.2006.11.004.
21. M. Meyer, S. Dietrich, H. Schulz and A. Mondschein, Coatings, 2021, 11, 226,  DOI:10.3390/coatings11020226.
22. M. Javanshir, N. Chaari, A. M. Ibrahim and A. A. Abolhassani, J. Environ. Manage., 2024, 352, 120160,  DOI:10.3390/coatings11020226.
23. I. Quaratesi, E. Badea, I. Calinescu, N. P. Sardroudi, G. Zengin and C. Casas, et al. , Appl. Sci., 2024, 14, 10263,  DOI:10.3390/app142210263.
24. M. G. Nor Afiqah, C. W. Liew, M. N. Zainal Abidin, A. A. A. Adnan and M. R. Ahmad, Food Bioprocess Technol., 2025, 18, 1577–1591,  DOI:10.3390/app142210263.
25. Y. Zhang, Y. Tian, C. He, C. Jin, L. Zhang and Z. Qian, LWT – Food Sci. Technol., 2022, 154, 112868,  DOI:10.1007/s11947-024-03642-3.
26. P. Gündoğan, Life Cycle Assessment of Leather and Leather-Like Materials, Master's thesis, KTH Royal Institute of Technology, 2024 DOI:10.1007/s11367-024-02351-5.
27. J. Masih and R. Priyanka, J. Exp. Agric. Int., 2016, 12(1), 476,  DOI:10.9734/AJEA/2016/24737.
28. Y. Deng, W. M. J. Achten, K. Van Acker and J. R. Duflou, Biofuels, Bioprod. Biorefin., 2013, 7, 429–458,  DOI:10.1002/bbb.1406.
29. A. M. Ferreira, S. Fiore and M. Matarazzo, J. Cleaner Prod., 2021, 320, 128702,  DOI:10.1016/J.JCLEPRO.2019.03.335.
30. A. Thévenot, M. Maillard, O. Rosenbaum, A. Farges and G. Bellon-Maurel, J. Cleaner Prod., 2018, 170, 1260–1277,  DOI:10.1186/s42825-020-00035-y.
31. H. Jung, B. H. Park, J. H. Kim and D. X. Oh, J. Hazard. Mater. Adv., 2023, 10, 100311,  DOI:10.1021/bm200009h.
32. J. Yu, W. Wei, E. Danner, R. K. Ashley, J. N. Israelachvili and J. H. Waite, Nat. Chem. Biol., 2011, 7, 588–590,  DOI:10.1038/nchembio.630.
33. S. M. Kim, M. H. Kim, S. Y. Yang, S. Y. Kim, D. S. Hwang and J. Y. Sun, J. Mater. Chem. A, 2023, 11, 21232–21241,  10.1039/D3TA03811D.
34. A. Miserez, T. Schneberk, C. Sun, F. W. Zok and J. H. Waite, Science, 2008, 319, 1816–1819,  DOI:10.1126/science.1154117.
35. S. C. T. Nicklisch, J. J. Waite, A. J. Israelachvili and K. H. Healy, Biofouling, 2012, 28, 835–842,  DOI:10.1080/08927014.2012.719023.
36. D. X. Oh, E. Prajatelistia, S. W. Ju, H. J. Kim, H. S. Rho and S. H. Hwang, et al. , Sci. Rep., 2015, 5, 10884,  DOI:10.1038/srep10884.
37. L. T. Hao, S. Ju, D. K. Hwang and D. S. Hwang, Nat. Rev. Bioeng., 2024, 2, 1–14,  DOI:10.1038/s44222-023-00142-5.
38. Z.-M. Li, Y.-X. Zhang, H.-R. Wang, L.-Y. Chen, Y.-N. Wu and X.-M. Lu, Mater. Horiz., 2025, 12, eD4MH01203H,  10.1039/D4MH01203H.
39. L. Huang, C. Chen, Y. Zheng, Z. Wang, Y. Xu and H. Zeng, Mater. Horiz., 2024, 11, 1966–1980,  10.1039/D3MH01998E.
40. Z. Li, J. Wu, K. Sun, K. Tao, X. Zhou and K. Liu, et al. , Adv. Mater., 2021, 33, 2101498,  DOI:10.1002/adma.202101498.
41. H. Wang, J. Zhao, J. Wu, X. Zhang and W. Huang, CCS Chem., 2024, 6, 1595–1603.
42. J.-H. Chung and J.-H. Oh, Mater. Horiz., 2025, 12, 4573–4607,  10.1039/D4MH01757A.
43. D. A. Malencik and S. R. Anderson, Amino Acids, 2003, 25, 233–247,  DOI:10.1007/s00726-003-0014-z.
44. A. Kamada, M. Rodriguez-Garcia, F. S. Ruggeri, Y. Shen, A. Levin and T. P. J. Knowles, Nat. Commun., 2021, 12, 3707,  DOI:10.1038/s41467-021-23813-6.
45. H. Kim, J. E. Song and H. R. Kim, Cellulose, 2021, 28, 3183–3200,  DOI:10.1007/s10570-021-03705-0.
46. M. Y. Pamukoglu and M. C. Karabuga, Environ. Eng. Sci., 2017, 35, 703–709,  DOI:10.1089/ees.2017.0372.
47. M. Y. Pamukoglu, B. Kirkan and M. Senyurt, J. Radioanal. Nucl. Chem., 2017, 314, 343–352,  DOI:10.1007/s10967-017-5349-0.
48. M. Henke, B. Lis and T. Krystofiak, Materials, 2023, 16, 4468,  DOI:10.3390/ma16124468.
49. P. Patil, S. F. Abbas, S. D. Jadhav and P. M. Koli, J. Compos. Sci., 2023, 7, 513,  DOI:10.3390/jcs7050513.

---