Silk fibroin (recombinant, biomaterials)

01Overview and value chain

Markers: [EC: FDA 510(k) Medical Device Pathway / EU Industrial Biotechnology & REACH / NMPA Biological Materials Approval | OECD: Bio-based materials | Regulator: FDA (USA), EMA (EU), NMPA (China)]

Recombinant silk fibroin and spider-silk proteins replace two constrained traditional sources — harvest from territorial, cannibalistic spiders (impractical at scale, ~30-80 meters of silk per session before the spider must rest) and extraction from Bombyx mori silkworm cocoons (limited by batch variability, potential immunogenicity, and downstream purification burden) — with biosynthetic production of the structural silk protein in microbial, mammalian, or transgenic-animal hosts. Three dominant production platforms emerged by 2026: microbial precision fermentation of engineered bacteria or yeast expressing spider-silk protein sequences (Spiber’s Brewed Protein™ from sugarcane-fed microbes, AMSilk’s Biosteel via 21st.BIO-developed strains, Bolt Threads’ MicroSilk from genetically engineered yeast); transgenic Bombyx mori silkworms expressing dragline spider-silk proteins MaSp1 and MaSp2 alongside the silkworm’s native fiber (Kraig Biocraft Laboratories, leveraging millennia-old Southeast Asian sericulture infrastructure); and purified Bombyx mori silk fibroin processed into biomaterials for medical devices (Sofregen Medical’s SilkVoice vocal-cord medialization, FDA-cleared). The natural material benchmark is impressive — by weight spider silk can be stronger than steel and tougher than many high-performance synthetic materials, with Kraig Biocraft’s laboratory-verified transgenic fibers reaching tensile strengths around 1.8 gigapascals and elasticity above 38% — but commercialization turned on yield, and 2026 marked the procurement-readiness transition: Kraig Biocraft produced over 1.3 metric tons of recombinant spider silk cocoons in March 2026 (1.8 MT in April, with yields exceeding targets by 20% in May), putting the material within the volume range at which defense contractors, medical device manufacturers, and aerospace suppliers can begin material-qualification testing. On the textile side, Spiber’s Rayong Thailand factory (operating since 2022 at several hundred tonnes/year, ~100x the Japan plant output) and 2025 European-mill partnerships produced 100% Brewed Protein™ yarns, while AMSilk’s bioengineered yarns debuted in Balenciaga’s Spring 2026 collection and the company’s dedicated 160 m³ Nesle France fermentation plant (via Ajinomoto Foods Europe) came online in July 2026. Sofregen Medical’s SilkVoice holds FDA 510(k) clearances K180631 (November 2018) and K240919 (May 2024) for silk fibroin vocal-cord medialization, with an independent 33-patient Laryngoscope 2026 study reporting 86.2% of patients with at least minimal vocal improvement. Bolt Threads patented recombinant silk polypeptide as a silicone replacement in personal care (US20260069524A1, published March 2026), with a shampoo formulation using 0.05 wt% silk polypeptide replacing 3 wt% silicone elastomer.

The key directions of recombinant silk fibroin are:

1. Microbial precision fermentation of spider silk (Brewed Protein™ / Biosteel / MicroSilk): Spiber’s Brewed Protein™ — precision-fermented microbes from sugarcane plant sugars, first major factory in Rayong Thailand (2022) at several hundred tonnes/year, $489M total funding ($65M raised January 2025), plan to exceed 1,000 tonnes/year by 2026, partnerships with Goldwin/The North Face (Moon Parka 2019), Botto Giuseppe (January 2025, first 100% Brewed Protein yarn from a European mill), Manifattura Sesia + Achille Pinto (June 2025), 100% Brewed Protein material unveiled at Pitti Immagine Filati + Milano Unica (June 2026); AMSilk’s Biosteel — Balenciaga Spring 2026 collection (January 2026), Ajinomoto Foods Europe dedicated 160 m³ Nesle France plant (July 2026), AMSilk4Shine + AMSilk4Care consumer care launch (June 2025).
2. Transgenic Bombyx mori silkworm expression (MaSp1 / MaSp2): Kraig Biocraft Laboratories (OTCQB: KBLB) — genetically engineered silkworms expressing dragline spider-silk proteins MaSp1 and MaSp2 alongside native silk fiber; 1 million engineered silkworm eggs deployed in Vietnam (March 2026), 1.3 MT/month cocoons in March 2026 (5x previous record), 1.8 MT in April 2026, yields exceeding targets by 20% in May 2026, tensile strength ~1.8 GPa and elasticity >38%, target 10 MT/month at full scale; featured on National Geographic March 2026 cover; PNAS peer-reviewed validation.
3. Recombinant silk polypeptide as silicone replacement (personal care): Bolt Threads (Emeryville CA, founded 2009, co-founders Dan Widmaier and David Breslauer) — patent US20260069524A1 published March 12, 2026 covering recombinant silk polypeptides as a silicone (fluid and elastomer) replacement in beauty and personal care formulations, with shampoo using 0.05 wt% silk polypeptide replacing 3 wt% silicone elastomer; biodegradable alternative to non-biodegradable silicone elastomers across SPF, color cosmetics, washes, serums, primers, shampoos.
4. Silk fibroin biomaterials for medical devices: Sofregen Medical (Framingham/Medford MA) — SilkVoice silk fibroin vocal-cord medialization device, FDA 510(k) clearances K180631 (November 8, 2018, traditional pathway) and K240919 (May 3, 2024, Special 510(k) for SMI-04, 30-day review), Class II ENT device under product code MIX (21 CFR 874.3620); silk-HA injection laryngoplasty validated in 33-patient Laryngoscope 2026 study (44 silk-HA injections, 86.2% with at least minimal vocal improvement, mean age 73.4, 79.3% partial-to-significant improvement).

Sectoral value chain

[spider-silk gene construct (MaSp1/MaSp2) / silk fibroin gene / Bombyx mori silkworm] ──> [microbial fermentation / transgenic silkworm cocoon / cocoon extraction]
                                                                                              │
                                                                          (raw silk protein / cocoon)
                                                                                              │
                                                                                              ▼
[finished fiber, yarn, biomaterial device, or ingredient] <─── [textile spinning / purification / device formulation] <─── [downstream chromatographic purification]

Value chain levels

Cross-cutting technologies of the sector:

• Microbial precision fermentation of spider silk (Microbial Precision Fermentation Spider Silk / Brewed Protein): Spiber’s Brewed Protein™ — the only protein fibre (per ISO 2076) made through precision fermentation available at industrial scale, using sugarcane-fed engineered microbes, with measured environmental savings of up to 75% GHG versus cashmere, 94% less water, and 86% less land; AMSilk’s 21st.BIO-developed strains and Bolt Threads’ yeast fermentation round out the platform.
• Transgenic Bombyx mori silkworm expression (Transgenic Bombyx mori Silkworm Expression): Kraig Biocraft’s approach inserts MaSp1/MaSp2 spider-silk gene cassettes into the domesticated silkworm — an animal farmed industrially for millennia — inheriting the entire sericulture infrastructure (mulberry cultivation, rearing sheds, cocoon reeling) already concentrated in Southeast Asia; the silkworm’s natural spinning apparatus produces the fiber, eliminating the wet-spinning bottleneck of microbial routes.
• Silk fibroin biomaterials for medical devices (Silk Fibroin Biomaterial Medical Device): Sofregen Medical’s SilkVoice uses purified Bombyx mori silk fibroin (the 66.5 kDa protein fraction) formulated as an injectable hydrogel for vocal-cord medialization, regulated under FDA’s 510(k) Class II ENT device pathway — distinct from the textile and personal-care applications but the regulatory template for the broader silk fibroin biomaterials field (wound dressings, surgical sutures, tissue-engineering scaffolds, drug-delivery matrices).

02US

The US hosts the largest transgenic-silkworm spider silk producer (Kraig Biocraft, with Vietnam production), the original microbial spider silk developer (Bolt Threads), and the only FDA-cleared silk fibroin medical device manufacturer (Sofregen Medical) — with the FDA’s 510(k) Class II device pathway and the USPTO patent system governing the field.

Kraig transgenic silkworm scale-up, Bolt silicone-replacement patent, Sofregen FDA 510(k)

• Kraig Biocraft Laboratories (Ann Arbor MI, OTCQB: KBLB, founder/CEO Kim Thompson): engineered Bombyx mori silkworms expressing dragline spider-silk proteins MaSp1 and MaSp2 alongside the silkworm’s native fiber; 1 million engineered silkworm eggs deployed across multiple production facilities in Vietnam (announced March 18, 2026), with cocoon production hitting 1.3 metric tons in March 2026 (5x previous record, announced April 6), 1.8 MT in April 2026, and yields exceeding targets by 20% in May 2026; target roughly 10 MT/month at full scale; laboratory-verified tensile strength ~1.8 GPa with elasticity above 38%; PNAS peer-reviewed validation; National Geographic March 2026 cover story; preparing initial pilot shipments to several undisclosed global brands for defense, medical device, and aerospace material-qualification testing.
• Bolt Threads (Emeryville CA, founded 2009, co-founders Dan Widmaier and David Breslauer): MicroSilk regenerated protein fibre mimicking spider silk, fermented from water, yeast, sugar, and spider DNA, then spun through spinnerets like acrylic or rayon; $40 million in investments and government grants (including NSF); patent US20260069524A1 published March 12, 2026 covering recombinant silk polypeptides as a silicone (fluid and elastomer) replacement in beauty and personal care formulations — shampoo using 0.05 wt% silk polypeptide replacing 3 wt% silicone elastomer, biodegradable alternative to non-biodegradable silicone elastomers across SPF formulations, color cosmetics, washes, serums, primers, and shampoos.
• Sofregen Medical (Framingham/Medford MA): SilkVoice silk fibroin vocal-cord medialization device, the only FDA-cleared silk fibroin ENT device on the US market — Class II under product code MIX (System, Vocal Cord Medialization) and 21 CFR 874.3620; K180631 cleared November 8, 2018 via the Traditional 510(k) pathway (244-day review); K240919 (Silk Voice SMI-04) cleared May 3, 2024 via the Special 510(k) pathway (30-day review, 59 days faster than the panel average); validated in an independent 33-patient Silk-Hyaluronic Acid Laryngoplasty study (Laryngoscope 2026, 44 silk-HA injections between June 2022 and August 2025, mean age 73.4 years, 86.2% with at least minimal vocal improvement, 79.3% partial-to-significant improvement).

03CN

China is the world’s largest Bombyx mori silk producer and the academic anchor for silk-fibroin biomaterials research in tissue engineering, drug delivery, and wound dressings — but no Chinese recombinant silk firm has reached the commercial scale of Spiber, AMSilk, or Kraig as of 2026.

Bombyx mori production base, academic biomaterials research, industry participants

• Academic anchor (Xia Qingyou team, Southwest University): the Xia Qingyou team at Southwest University’s Frontiers Interdisciplinary Research Center Biology Research Center published the Advanced Materials cover paper “An Efficient Biosynthetic System for Developing Functional Silk Fibroin-Based Biomaterials” — the Fib-HEXP silkworm gland biosynthetic system that successfully synthesized recombinant red fluorescent protein (RFP) at ~7.86% of silk mass in the cocoon, demonstrating the genetic functionalization of silk fibroin for custom bioactive properties (vascularization-promoting, antibacterial, immunomodulatory) — a key enabler for next-generation Chinese recombinant silk fibroin biomaterials.
• East China University of Science and Technology (ECUST) Pichia pastoris work: the ECUST team overcame protein degradation, translational stalling, and intracellular aggregation to achieve high-efficiency secreted production of recombinant silk fibroin via engineered Pichia pastoris yeast, converting it into functional nanomaterials — the microbial-fermentation alternative to the silkworm route, joining Zhejiang University, Soochow University, Donghua University, and China Agricultural University as the Chinese academic research base.
• Industry participants (per the 2025-2029 Xinshijie industry report): Chinese silk fibroin biomaterials market participants named as important players include 浙江星月生物科技股份有限公司 (Zhejiang Xingyue Biotech), 复向丝泰医疗科技(苏州)有限公司 (Fuxiang Sitai Medical Tech Suzhou), 苏州苏豪生物材料科技有限公司 (Suzhou Suhao Biomaterials, founded 2006 by Jiangsu Suhao International Group), 湖北赛罗生物材料有限公司 (Hubei Sailuo Biomaterials), and 吉林省国大生物工程有限公司 (Jilin Guoda Bioengineering) — no Chinese recombinant silk firm has yet surfaced a specific 2026 commercial event on the scale of the Spiber, AMSilk, Kraig, or Sofregen milestones; silk fibroin is included in China’s 14th Five-Year Plan “diagnostic equipment and biomedical materials” key special project alongside chitosan and cell matrix materials, positioning the field for sustained policy support.

04EU

The EU hosts the leading biotech-produced spider silk biomaterials firm outside Japan (AMSilk in Neuried Germany), has attracted Japanese producer Spiber’s European-mill partnerships (Italy), and is the target market for scale-up manufacturing via the Ajinomoto Foods Europe dedicated fermentation plant in Nesle France.

AMSilk Balenciaga launch, Ajinomoto Nesle France plant, Spiber Italian mill partnerships

• AMSilk (Neuried near Munich, CEO Ulrich Scherbel): global leader in advanced biomaterials from spider silk-based proteins, industrial-scale supplier since 2015; bioengineered yarns debuted in Balenciaga’s Spring 2026 collection (January 21, 2026 — a white shirt and black shirtdress in select Balenciaga stores worldwide); Ajinomoto Foods Europe (AFE) expanded partnership (July 8, 2026) establishing a dedicated silk-protein production line at AFE’s Nesle France biomanufacturing site with 160 m³ fermentation reactor capacity, “Made in France” positioning, multi-million joint investment; 21st.BIO (Copenhagen) strain-development partnership (January 17, 2024) for precision-fermentation scale-up; BRAIN Biotech protein-engineering collaboration (March 5, 2024, first PCT patent filed); AMSilk4Shine + AMSilk4Care consumer-care ingredient launch (June 10, 2025) targeting silicone and petroleum-polymer replacement in rinse-aid, screen/window cleaner, and personal-care formulations.
• Spiber Italian mill partnerships: Spiber (Yamagata Japan) extended its European textile supply chain through Botto Giuseppe (January 27, 2025 — first European mill to develop and market 100% Brewed Protein™ worsted yarn, plus 20-50% Brewed Protein + cashmere blends), Manifattura Sesia (June 26, 2025 — T-Gen 30% Brewed Protein + Superfine Merino Wool RWS/Nativa blends), and Achille Pinto (June 26, 2025 — 15-30% Brewed Protein + silk + wool blends, first European manufacturer to demonstrate printing on Brewed Protein fabrics, first textiles in Europe to combine Brewed Protein with silk); 100% Brewed Protein material unveiled at Pitti Immagine Filati (Florence, June 24-26, 2026) and Milano Unica (Rho Fiera Milano, July 7-9, 2026) for the Fall/Winter 2027/2028 season.
• EU regulatory framing: spider-silk fiber and silk-protein ingredients fall under the EU Industrial Biotechnology framework and REACH for chemical safety, with the EU’s microplastics-reduction action plan (30% reduction target by 2030) explicitly driving demand for AMSilk’s biodegradable, microplastic-free silk protein ingredients as replacements for petroleum-based polymers in consumer-care and textile formulations.

05Leading companies and research institutes

06Tech stack and innovations

The recombinant silk stack rests on three orthogonal production platforms — microbial precision fermentation, transgenic Bombyx mori silkworm expression, and purified Bombyx mori fibroin biomaterial formulation — each with a distinct scale, cost, and regulatory profile.

1. Microbial precision fermentation of spider silk (Microbial Precision Fermentation Spider Silk / Brewed Protein):
   • Spiber designs custom protein sequences in silico, programs microbes (bacteria or yeast) to express them from sugarcane plant sugars in a fermentation tank, then spins the protein into fiber; the platform is the only protein fibre (ISO 2076) made through precision fermentation available at industrial scale, with the Rayong Thailand plant reaching several hundred tonnes per year (~100x the original Japan pilot) and a stated plan to exceed 1,000 tonnes/year by 2026 on non-food renewable inputs.
   • AMSilk partnered with 21st.BIO (Copenhagen, January 2024) to develop a new precision-fermentation production strain using highly specialized microorganisms for extracellular spider silk protein expression, then with Ajinomoto Foods Europe (July 2026) to commission a dedicated 160 m³ fermentation reactor at the Nesle France biomanufacturing site — bringing the microbial route from kilograms to hundreds-of-tonnes-per-year commercial scale.
2. Transgenic Bombyx mori silkworm expression (Transgenic Bombyx mori Silkworm Expression MaSp1/MaSp2):
   • Kraig Biocraft’s platform inserts dragline spider-silk gene cassettes (MaSp1 and MaSp2) into the domesticated Bombyx mori silkworm — an animal farmed industrially for millennia across Southeast Asia — so the silkworm’s natural spinning apparatus produces a composite fiber containing both native silk and the spider-silk proteins, inheriting the existing mulberry cultivation, rearing shed, and cocoon reeling infrastructure rather than requiring new bioreactor CapEx.
   • The 1 million engineered silkworm eggs deployed in Vietnam (March 2026) and the March-to-May 2026 production cycle (1.3 MT → 1.8 MT → 20% beat on yield targets) demonstrated the platform’s procurement-readiness for defense contractors, medical device manufacturers, and aerospace suppliers — the volume range at which material-qualification testing becomes practical; PNAS peer-reviewed validation confirmed composite fibers tougher than conventional silkworm silk and approaching natural dragline spider silk.
3. Silk fibroin biomaterials for medical devices (Silk Fibroin Biomaterial Medical Device):
   • Sofregen Medical’s SilkVoice uses purified Bombyx mori silk fibroin (the 66.5 kDa H-chain + L-chain protein fraction, isolated from cocoons via degumming to remove sericin and controlled dissolution) formulated as an injectable silk-HA hydrogel for vocal-cord medialization; cleared as an FDA Class II ENT device under product code MIX (21 CFR 874.3620) via the Traditional 510(k) pathway (K180631, 2018) and updated via Special 510(k) (K240919, 2024).
   • The Laryngoscope 2026 study (33 patients, 44 silk-HA injections, June 2022-August 2025 retrospective) provides independent external validation: 86.2% reported at least minimal vocal improvement, 79.3% partial-to-significant improvement, median improvement scores equivalent to prior HA injection in within-patient comparison (p=0.776), with higher operative revision rates (6.8% vs 0.6% historical HA cohort) attributable to elective overaugmentation revisions — establishing silk fibroin as a viable office-based injection laryngoplasty option.

07Value chains and production pipelines

Industrial pipeline of recombinant silk fibroin & spider silk (FDA 510(k) / EU Industrial Biotechnology / NMPA biomaterials)

┌───────────────────────────┐      ┌───────────────────────────┐
│ 1. Strain & construct     │ ───> │ 2. Upstream expression    │
│    (MaSp1/MaSp2 cassette  │      │    (microbial bioreactor  │
│    or Bombyx mori eggs)   │      │    or silkworm rearing)   │
└───────────────────────────┘      └───────────────────────────┘
                                                  │
                                                  ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 4. Chromatographic        │ <─── │ 3. Harvest /              │
│    purification /         │      │    cocoon reeling &       │
│    degumming              │      │    degumming              │
└───────────────────────────┘      └───────────────────────────┘
              │
              ▼
┌───────────────────────────┐      ┌───────────────────────────┐
│ 5. Spinning /             │ ───> │ 6. Textile / device       │
│    formulation            │      │    conversion             │
└───────────────────────────┘      └───────────────────────────┘

Stage 1: Strain & construct

The spider-silk gene cassette (MaSp1 and MaSp2 dragline proteins for Kraig Biocraft’s transgenic silkworm route; custom-designed silk protein sequences for Spiber’s Brewed Protein™ and AMSilk’s Biosteel; spider DNA + yeast expression vector for Bolt Threads’ MicroSilk) is inserted into the host — microbial master cell bank (Spiber, AMSilk, Bolt) or genetically engineered Bombyx mori silkworm eggs (Kraig, 1 million eggs deployed in Vietnam).

Stage 2: Upstream expression

Microbial precision fermentation runs in stainless or single-use bioreactors on sugarcane-derived sugar feedstock (Spiber Rayong Thailand several hundred tonnes/year; AMSilk Ajinomoto 160 m³ Nesle France plant via the July 2026 expanded partnership; Bolt Threads yeast fermentation with $40M NSF-backed capex); alternatively, transgenic silkworms are reared on mulberry leaves across Vietnam production facilities following millennia-old sericulture practice, with each engineered silkworm spinning a cocoon containing composite native + spider-silk fiber.

Stage 3: Harvest / cocoon reeling & degumming

Microbial biomass is lysed (mechanically or enzymatically) to release intracellular silk protein; transgenic silkworm cocoons are reeled into continuous fiber (Kraig reported ~50% conversion of the April 2026 1.8 MT cocoon batch into reeled silk by April 28, 2026); traditional Bombyx mori cocoons for biomaterial use are degummed to remove the ~25% sericin outer protein, leaving the ~75% silk fibroin inner fiber (H-chain + L-chain + P25 complex).

Stage 4: Chromatographic purification / degumming

Microbial-route silk protein is purified via affinity, ion-exchange, and hydrophobic-interaction chromatography to remove host-cell proteins, nucleic acids, and endotoxins (AMSilk’s customized downstream processing at Nesle France; Spiber’s OryzPur-equivalent purification); Bombyx-route fibroin is dissolved in LiBr or similar chaotropic solvent, then dialyzed into aqueous regenerated fibroin solution for biomaterial casting (Sofregen SilkVoice hydrogel precursor).

Stage 5: Spinning / formulation

Purified silk protein is wet-spun or microfluidically spun into fiber (Spiber, AMSilk, Bolt Threads), matching the spinning dynamics of acrylic and rayon processes; reeled transgenic silk is spun directly into yarn by the silkworm and prepared for textile weaving (Kraig); regenerated fibroin solution is formulated into an injectable silk-HA hydrogel (Sofregen SilkVoice), cast as a film/scaffold, or freeze-dried as a personal-care ingredient powder (Bolt Threads’ silicone-replacement polypeptide).

Stage 6: Textile / device conversion

Spun fiber is converted into yarn (Spiber + Botto Giuseppe 100% Brewed Protein worsted yarn; AMSilk + Balenciaga Spring 2026 yarns; Kraig reeled spider silk for defense/aerospace), woven/knitted into textile, and shipped to brand partners for garment manufacturing; Sofregen Medical’s SilkVoice hydrogel is filled into single-use injection devices, FDA-cleared under 510(k) K180631/K240919, and distributed to ENT specialists for office-based vocal-cord medialization; Bolt Threads’ silk polypeptide ingredient is supplied to beauty and personal-care formulators as a biodegradable silicone replacement under the US20260069524A1 patent.