US 7000000

I'll verify the patent details against live sources before summarizing.

US Patent 7,000,000 — Summary

Verification note: I searched for this number in live sources (Google Patents, EPO publication server, C&EN, Textile World, PubChem for the EP family member) and in Federal Circuit 2026 docket materials. All sources confirm the patent's identity. I found no CAFC (or district court) 2026 litigation involving U.S. Patent 7,000,000 — the 2026 docket/opinion items I retrieved involve unrelated patents (e.g., the "700 patent" in Constellation Designs v. LG is U.S. 10,693,700, a different number). I cannot confirm from these searches that patent 7,000,000 has ever been litigated at the Federal Circuit; treat "no CAFC activity found" as a search result, not proof of absence.

Bibliographic data

Abstract (as issued)

"This invention pertains to novel fibers made of α(1→3) polysaccharides, and a process for their production. The fibers of the invention have 'cotton-like' properties but can be produced as continuous filaments on a year-round basis. The fibers are useful in textile applications."

Overview of the independent claims

The patent has 15 claims, of which three are independent — one product claim, one process claim, and one composition claim.

Claim 1 — the fiber (product). A polysaccharide fiber made of a polymer containing hexose (sugar) units, where at least 50% of those units are joined by an α(1→3) glycoside linkage, the polymer having a number-average degree of polymerization of at least 100 (i.e., at least ~100 sugar rings per chain on average), and the fiber exhibiting a tensile strength of at least 1 gram per denier. In plain terms: a spun textile fiber whose backbone chemistry is dominantly α(1→3)-linked, and which is strong enough to be a practical fiber rather than a weak film. Dependent claims 2 and 3 narrow this to substantially all (≥90%) α(1→3) linkages and to poly(α(1→3)-D-glucose), respectively.

Claim 4 — the process (spinning). A method of making such a fiber by (a) dissolving enough of the α(1→3)-linked hexose polymer in a solvent (or solvent mixture) to form a liquid crystalline solution having a solids content of at least 20%, and (b) spinning a fiber from that liquid crystalline solution. The core insight is that α(1→3) glucans, contrary to prior teaching that only β(1→4) backbones are rigid enough, will form an ordered (lyotropic) phase at practical concentrations and can be wet-spun or air-gap spun into oriented filament. Note the claim's ≥20% solids floor is higher than the ~10% figure described as merely preferred in the specification, and the specification states the observed onset for 100% poly(α(1→3)-D-glucose) (Mn ≈60,000 Da) in 60/40 TFA/CH₂Cl₂ is about 15% — so the claim sits above the disclosed minimum. Dependent claims add: substantially all α(1→3) (5); derivatizing the polymer before dissolving (6); acetylation (7); specifically poly(α(1→3)-D-glucose acetate) (8); regenerating by contacting the fiber with excess saponification/hydrolysis medium (9); solvent selected from organic acids, organic halides, fluorinated alcohols, and mixtures (10); and solids content of 20–35% (11).

Claim 12 — the liquid crystalline solution (composition). A solution comprising a solvent plus enough of the α(1→3)-linked hexose polymer to form liquid crystals, with the polymer amount giving a solids content of at least 20%. This claims the spin dope itself, independent of any spinning step. Dependent claims 13–15 narrow to substantially all α(1→3) linkages, poly(α(1→3)-D-glucose acetate), and the solvent group, respectively.

Practical context

• The specification identifies the polymer source as a glucan made by contacting aqueous sucrose with GtfJ glucosyltransferase from Streptococcus salivarius (Simpson et al., Microbiology 141:1451–1460 (1995)), with the gtf-J gene cloned from strain ATCC 25975 by PCR.
• Working examples report as-spun fiber tenacities up to 4.2 g/denier (Example 1, air-gap spun into methanol from a 35% solids TFA/water dope) and 2.4–2.7 g/denier after deacetylation. Comparative examples with α(1→4) (debranched amylose) glucan acetate gave non-liquid-crystalline dopes and fibers at 0.3–0.5 g/denier, supporting the α(1→3) enchainment as the critical feature.
• Example 7 shows nigeran (alternating α(1→3)/α(1→4)) also forms a birefringent, liquid crystalline solution, consistent with the ≥50% limitation.
• This patent is the foundational family member for DuPont's later poly-α-1,3-glucan fiber program; numerous later DuPont and Lenzing filings (e.g., WO 2013/052730, WO 2013/177348, WO 2014/161018) expressly cite O'Brien, U.S. Patent No. 7,000,000 as background.

Uncertainties

• I did not retrieve a USPTO Patent Center/assignment record directly; assignee and legal-status values above come from Google Patents' aggregation and are flagged there as assumptions rather than legal conclusions. Confirm current ownership and expiration (including any §154(b) term adjustment) against USPTO PatentCenter if this matters.
• The Google Patents rendering of the claim set shows "at least 20%" in claims 4 and 12; the specification's preferred minimum is 10%, with 15% reported as the observed phase-separation threshold for the specific polymer tested. That gap is real in the issued text, but if you need the truly authoritative claim wording, pull the granted patent PDF rather than the HTML rendering.
• No evidence of 2026 CAFC activity on this patent was found; that is a negative search result, not confirmation that no such proceeding exists or has existed.

I'll search for litigation involving US patent 7000000.

Let me search additional litigation-specific sources.

Let me run more targeted searches on litigation databases.

Summary of Findings

No litigation involving U.S. Patent No. 7,000,000 was identified in my searches. I was unable to locate any district court action, ITC investigation, or PTAB proceeding (IPR/PGR/CBM) naming US 7,000,000 as an asserted or challenged patent.

Basis for This Conclusion

I searched litigation-oriented sources (including the Unified Patents portal/caselist, Docket Alarm, Justia dockets and case law, RPX litigation documents, and general web queries targeting the specific number) but did not reach the specific patent record within my tool budget; the searches I did complete returned no case citing US 7,000,000 as a patent-in-suit. Specifically:

• Queries combining "7000000" with litigation/PTAB/unifiedpatents returned results about other patents (e.g., Polaris PowerLED '117 patent, MCOM IP '508 patent, VideoLabs '794 patent, Dolby '577 patent) — none involving US 7,000,000.
• Queries for "US 7,000,000" / "patent 7,000,000" returned only prosecution and specification citations (e.g., US 10,774,352; US 2016/0333157; US 9,365,955; EP 3,870,616; US 9,034,092), where US 7,000,000 is cited as background art or incorporated by reference — articles of manufacture, not litigation.
• The Google Patents page for US 7,000,000 (as provided in the authoritative record) lists 208 "Cited By" entries, all of which are patent documents, with no litigation section.

Case Table

Important Caveats

1. I could not confirm the absence with the certainty of a full docket search. My tool budget was exhausted before I could query PACER directly, or Docket Alarm / RPX / Unified Patents case lists with a patent-number filter. The absence of hits in my searches is evidence of no litigation, but not proof.
2. This is a real, expired patent. Per the authoritative record, US 7,000,000 B1 ("Polysaccharide fibers," John P. O'Brien, originally assigned to E. I. Du Pont de Nemours and Company) issued 2006‑02‑14 and reached anticipated expiration on 2020‑01‑19 (status: "Expired – Lifetime"). Any enforcement window would have been 2006–2020. A patent that expired unasserted would be entirely consistent with what I found.
3. The relevant patent family/technology was actively developed by DuPont, and many later DuPont/IPR-adjacent filings cite US 7,000,000 (e.g., high-titer poly(α‑1,3‑glucan) production, glucosyltransferase enzymes). But citation-by-examiner and incorporation-by-reference are not litigation and should not be reported as such.

Recommended Verification Steps (if you need a definitive answer)

To establish a firm "no litigation" conclusion, I suggest checking directly:

• PACER – run a party search on "E. I. du Pont de Nemours" and a patent-number search on 7,000,000 across district courts.
• Docket Alarm (https://www.docketalarm.com) – patent-level docket lookup.
• Unified Patents Portal (https://portal.unifiedpatents.com/litigation/caselist) and the PTAB caselist, filtered by patent number.
• USPTO Patent Center / Global Dossier for the '000 patent's "Litigation" tab (which would list any suits involving the patent).

If you'd like, I can attempt a more targeted query (e.g., a specific PACER-style party + patent-number combination) when tool availability permits.

I'll verify the ODP default against public sources before writing this up.

PTAB Proceedings Report — US Patent 7,000,000 ("Polysaccharide fibers")

Proceedings overview

Total AIA trial proceedings on file for US 7,000,000: zero. The USPTO Open Data Portal structured block (the canonical source for this task) returns no IPR, PGR, or CBM proceedings, and my independent searches of PTAB decision materials surfaced no petition, institution decision, or Final Written Decision naming this patent. The breakdown is therefore 0 active / 0 claims invalidated / 0 claims sustained / 0 settled / 0 institution-denied — meaning all 15 claims are UNTESTED and the bottom-line defensive posture is the unusual one: the patent has never been stress-tested at the Board, and it never will be in the ordinary course, because it expired on 2020-01-19 and the AIA trial windows are closed or practically foreclosed. That is a defensive opportunity, not a defensive problem: there is no § 315(e)(2) estoppel on the books against anyone, so the entire prior-art universe remains available if this patent is ever asserted for pre-expiration conduct.

Proceedings

None. There is no proceeding to describe.

The structured ODP data reports no AIA trial activity. My searches for PTAB petitions, institutions, FWDs, and Federal Circuit appeals referencing US 7,000,000 returned only (a) citing references in later DuPont glucan patents (e.g., US 10,774,352; US 9,644,322; US 11,118,312), and (b) an unrelated false positive — a 2026 Samsung petition styled Samsung Elecs. Co. v. Massively Broadband LLC, IPR2026-00086, challenging US 8,725,700, a different patent with a coincidentally similar number (docket PDF). Do not conflate the two — "8,725,700" ≠ "7,000,000."

I did not find any public record of this patent being asserted in a district court action. I cannot rule out an unindexed or settled assertion, and I did not exhaustively search PACER or state dockets; treat that as "no evidence found" rather than an affirmative negative.

Patent posture (context for the absence of PTAB activity)

Claim 1 covers a polysaccharide fiber of hexose units, ≥50% linked by α(1→3) glycoside linkage, DPn ≥ 100, and tensile strength ≥ 1 g/den. Claims 4–11 cover the spin-from-liquid-crystal process and recite a ≥ 20% solids content (with claim 11 reciting 20–35%). Claims 12–15 cover the liquid crystalline solution itself at ≥ 20% solids. Note for a challenger: the specification describes "at least 10%" solids as merely preferred and "about 20 to about 35%" as most preferred — the claims sit at 20%. That gap between the claimed floor and the specification's broadest disclosed floor is an untested written-description/§ 112 hook that no tribunal has ever adjudicated.

Source: US 7,000,000 on Google Patents.

Strategic summary

Canceled vs. sustained vs. untested. Nothing is canceled; nothing is sustained by the Board; all of claims 1–15 are untested. Because the patent has expired, a validity adjudication — if one ever happens — will occur in district court under 35 U.S.C. § 282 (or via an ex parte reexamination request), not via AIA trial. There is no PTAB record to cite, and no PTAB FWD disposition to quote.

Estoppel landscape. Zero § 315(e)(2) estoppel attaches to this patent, because no party ever filed an IPR/PGR on it. Any defendant facing an assertion for pre-expiration conduct has the full prior-art runway: § 102/§ 103 combinations, on-sale/public-use and § 112 defenses, plus the prosecution-history story in the 09/857,572 file wrapper. The adjacent DuPont glucan patents have been the subject of active third-party interest (Lenzing AG filings and various DuPont continuation filings appear throughout the "cited by" record), but estoppel is patent-specific — nothing that happened in a proceeding on a related glucan patent would bar grounds against 7,000,000.

Pattern signals. No repeat petitioner (there are no petitioners). No patent-owner PTAB appeals. No defensive aggregator — no Unified Patents or similar entity appears anywhere in the chain. This is the signature of a patent that was never commercially asserted: it issued as the 7,000,000th utility patent, sat in DuPont's portfolio, was cited as foundational prior art by a decade of later DuPont glucan filings, and lapsed with the rest of the term. Well-asserted patents attract IPRs; this one attracted none, and its expiration forecloses the post-grant route going forward.

Recommended next steps

1. If you are a defendant and the demand letter cites US 7,000,000: the absence of any PTAB record cuts both ways. You cannot point to a canceling FWD, because none exists. Your leverage is elsewhere — first, check the damages window. The patent expired 2020-01-19, so any recovery is limited to pre-expiration infringement, and a demand premised on ongoing or future activity is facially defective. Second, verify which patent number the assertion actually invokes. DuPont's glucan fiber/film family is dense (e.g., US 9,175,423; US 9,212,301; US 9,334,584; US 9,214,etc.), and 7,000,000 is frequently cited as background art in those patents — a demand letter citing it may be citing the wrong member of the chain.
2. If you want a post-grant avenue anyway: none is realistically available. PGR is barred (effective filing date 2000, well before 2013-03-16); CBM sunset on 2020-09-16 and a polysaccharide fiber patent would not qualify as a covered business method regardless; and while the Board retains discretion to institute an IPR on an expired patent where a live controversy exists, the practical value is low because the patentee cannot amend to survive art and post-expiration damages are unavailable. Budget for a § 282 district court invalidity case, not a PTAB filing.
3. Verify the negatives before you rely on them. Cross-check the USPTO Patent Trial and Appeal Board PTAB E2E / PTAB Decisions and the USPTO Open Data Portal for both "7,000,000" and "09/857,572," and confirm the expiration and maintenance-fee status in PatentCenter. I found no PTAB activity, but my search was web-based; the ODP block in your prompt is the authoritative statement of the negative, and I have treated it as controlling.

Uncertainty disclosure: I could not confirm from public sources whether the EP counterpart (EP 1165867 B1, DE 60009886 T2 per the family listing) ever faced EPO opposition, and I did not verify district-court docket history beyond general web searching. Both are worth a paid database check if you are relying on this report for a litigation decision.

I'll start by verifying the assignment records against live sources before writing anything.

Ownership reconstruction — US 7,000,000 ("Polysaccharide fibers")

Sources actually retrieved: the Google Patents full-text record supplied in the worker prompt (authoritative for this task), plus corroborating hits from Google Patents legal-events pages for sibling patents in the same DuPont glucan portfolio. I was not able to open the USPTO Assignment Center record itself (assignmentcenter.uspto.gov / assignment.uspto.gov did not return data through the search tool available to me). Everything below is grounded in the record text I did retrieve; where a reel/frame or correspondent is genuinely unknown to me, I say so rather than fill it in.

Inventors

Departure pattern: not present. O'Brien did not leave the original assignee around filing. He is the named inventor on the 2011–2015 DuPont poly(α1→3 glucan) fibre filings that cite this patent (e.g., WO 2013/052730, US 2015/0126730), i.e., he remained the DuPont inventor-of-record on the same technology line for ~15 years after this filing. No fire-sale-precursor pattern.

Single-inventor filings are unusual for a large corporate fibre portfolio, but nothing in the record ties that to ownership behaviour. Not a finding.

Original assignee

E. I. du Pont de Nemours and Company (issued patent face; DuPont in Google Patents' assignee field).

• Line of business: diversified science/chemicals; this patent sits in DuPont's industrial-biotechnology effort (biomass-derived materials — the same programme as Bio-PDO/Sorona). The fibres of claims 1–3 are enzymatic poly(α1→3)-D-glucan spun from a lyotropic dope.
• Product embodying the claims: DuPont appears to have taken the technology to pilot/pilot-commercial scale on the derivative family (poly α-1,3-glucan for home/personal care, films, fibrids, nonwovens) rather than shipping a textile fibre under this exact patent. The USPTO's own 2006 press framing was "cotton-like," degradable fibres, i.e., a promise, not a shipped textile product.
• Current status: the 1802-incorporated DuPont entity was restructured in 2019 (DowDuPont three-way separation into DuPont / Corteva / Dow). The operating Nutrition & Biosciences business was then combined with International Flavors & Fragrances (N&B/IFF combination completed 2021). The original assignor entity no longer owns this patent; it is not in bankruptcy.

Assignment timeline

Both entries below are recorded in the Google Patents legal-events/reassignment list for US 7,000,000 (the authoritative text supplied for this task). The record shows two substantive chain links plus one corrective.

• Executed 1999/2000 (date of execution not shown) / recorded 2001-06-08 — Reel/Frame not exposed in the records I retrieved (Google Patents tags it simply "reassignment")

  • Conveyance: Assignment (of inventors' interest)
  • Assignor: O'BRIEN, JOHN P. (individually)
  • Assignee: E. I. DU PONT DE NEMOURS AND COMPANY
  • Correspondent: not stated in the retrieved record. For context only — and I flag this as not the recorded correspondent on this assignment — the agent of record on the sibling DuPont filing WO 2013/052730 is "HERRELL JR, Roger W., Legal Patent Records Center, 4417 Lancaster Pike, Wilmington DE," i.e., DuPont's in-house patent-records desk. Treat as unverified for this reel.
  • Context: standard employee-inventor assignment to the original corporate assignee. Recording date (2001) lags the 2000-01-19 PCT filing because US 09/857,572 is the §371 national-phase entry, filed mid-2001.

• Effective 2019-06-17 / recorded 2019-07-26 — Reel 049879/0043

  • Conveyance: Assignment
  • Assignor: E. I. du Pont de Nemours and Company
  • Assignee: DuPont Industrial Biosciences USA, LLC (Delaware)
  • Correspondent: not retrievable from the sources I could open. Flagging honestly: this is the single most useful field for an NPE analysis and I could not confirm it.
  • Context: internal corporate reorganisation — the carve-out of DuPont's industrial-biosciences/Nutrition & Biosciences business into a DuPont subsidiary ahead of the later IFF combination. Same reel/frame appears across the whole DuPont α-1,3-glucan portfolio (e.g., US 9,644,322; US 2017/0198109), i.e., a bulk portfolio schedule, not a patent-specific sale.

• Effective 2019-06-17 / recorded 2019-09-06 — Corrective assignment referencing Reel 049879/Frame 0043 (own reel/frame not shown in the US 7,000,000 record; the equivalent corrective for sibling patents in the same bulk transfer is recorded at Reel 050300/0408)

  • Conveyance: Correction — expressly "CORRECTIVE ASSIGNMENT TO CORRECT THE ENTITY TYPE PREVIOUSLY RECORDED AT REEL: 049879 FRAME: 0043"
  • Assignor: E. I. du Pont de Nemours and Company
  • Assignee: DuPont Industrial Biosciences USA, LLC
  • Correspondent: not retrievable.
  • Context: records correction only — fixes the entity type of the LLC; conveys no new interest.

Not present in the US 7,000,000 record, but present on siblings: Reel 055028/0496, DuPont Industrial Biosciences USA, LLC → Nutrition & Biosciences USA 4, Inc., effective 2020-07-01 (visible in the legal events of US 9,644,322 and US 11,028,187). The US 7,000,000 record I retrieved stops at the 2019-09-06 correction and then shows 2020-01-19 anticipated expiration / "Expired - Lifetime." Google Patents still lists the current assignee as DuPont Industrial Biosciences USA LLC. Whether US 7,000,000 was swept into reel 055028/0496 is unclear from the sources I could open — flag for verification against Assignment Center.

Timeline diagram

timeline
    title Ownership of US 7000000
    1999 : Priority date 25 Jan 1999
    2000 : PCT application filed 19 Jan 2000
    2001 : Assignment recorded to DuPont 8 Jun 2001
    2006 : Patent issued 14 Feb 2006
    2019 : Carve-out to DuPont Industrial Biosciences LLC
         : Corrective assignment recorded 6 Sep 2019
    2020 : Patent term expires 19 Jan 2020

NPE / troll-pattern signals

1. Shell-entity transfer — not present. Conveyance is to DuPont Industrial Biosciences USA, LLC, the operating legal entity for a large DuPont business unit, at Reel 049879/0043 (eff. 2019-06-17). The same reel/frame runs across dozens of DuPont glucan patents — the signature of a corporate carve-out schedule, not a single-purpose licensing vehicle. No evidence of a registered-agent address or a shell with no operations. (The signal "name suffix LLC" is not being treated as a finding, per your instruction.)

2. Known asserter in the chain — not present. No assignee in the chain matches Acacia, Marathon, IV, IPNav, Wi-LAN, Mosaid/Conversant, Vringo, Pendrell, Innovatio, MPHJ, Lumen View, Round Rock, Document Generation Corp, or Spangenberg entities. Chain is DuPont → DuPont subsidiary → (probably) Nutrition & Biosciences USA 4, Inc.

3. Repeat correspondent across the chain — unclear, not charged as a finding. I could not retrieve the recorded correspondent on Reel 049879/0043 or on the 2001 recording. I am not willing to name a correspondent from an unrelated prosecution record (Roger W. Herrell, Jr. / DuPont Legal Patent Records Center) and count it as recurrence. Verify in Assignment Center — if that desk recurs on both the 2001 and 2019 links, it is a benign in-house-records signature, not an NPE signal, since it does DuPont's own operating-company filings.

4. Cascading transfers — not present. The two 2019 recordings are ~6 weeks apart (2019-07-26 and 2019-09-06), but the second is expressly a correction of entity type, not a second transfer. One substantive conveyance in the chain, effective 2019-06-17.

5. Pre-litigation transfer — not present. My searches surfaced no infringement litigation naming US 7,000,000. The 2019-06-17 carve-out also is not 6-months-adjacent to any suit I could find, and it predates the patent's 2020-01-19 term expiry.

6. Bankruptcy fire-sale — not present. No Chapter 7/11 for E. I. du Pont de Nemours and Company in the record. 2019 events are a corporate separation, not a distressed sale.

7. Privateering — not present. No SEC-disclosed transfer to an NPE asserting on DuPont's behalf; no Patent Progress/EFF coverage tied to this patent. The transfer is intra-group.

8. Defensive aggregator — not present. Chain does not terminate at RPX, AST, LOT, Unified Patents, or OIN.

Additional dispositive fact: the patent expired 2020-01-19 (20-year term from the 2000-01-19 PCT filing), status "Expired - Lifetime" — it is not assertable today, which is why no asserter ever appears in the chain.

Verdict

Insufficient data — and specifically not an NPE pattern.

Justification: the only substantive post-issuance link is Reel 049879/0043 (effective 2019-06-17, recorded 2019-07-26), an intra-group carve-out of DuPont's industrial-biosciences business to DuPont Industrial Biosciences USA, LLC, paralleled across the entire DuPont α-1,3-glucan portfolio; the 2019-09-06 entry is a self-described corrective assignment correcting the entity type, not a transfer. Zero NPE signals are present (no known asserter, no litigation, no bankruptcy, no aggregator), and the patent's term ran out on 2020-01-19, so nothing in the chain required an asserter. The verdict is "insufficient data" rather than "operating-company assertion" or "defensive" only because the record I retrieved does not establish an operative product under claims 1–3 and does not confirm whether the later Nutrition & Biosciences USA 4, Inc. bulk assignment (Reel 055028/0496, eff. 2020-07-01) captured this patent.

Verification links: USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search by patent number 7000000); legacy search at https://assignment.uspto.gov/patent/index.html. Please re-pull Reel 049879/0043 and the 2001 recording there to capture the correspondent-of-record fields I could not verify — that is the one gap that would let a reader rule out signal 3 conclusively.

I'll research the prior art cited in US Patent 7,000,000.

Let me get the specific prior-art references cited on the face of US7000000 and its PCT/EP family members.

Let me get the exact face-of-patent references listed on US7000000 via FreePatentsOnline.

Prior-Art Analysis — U.S. Patent No. 7,000,000

Note on the ID: Interpreting literally, the identifier "7000000" resolves to US 7,000,000 B1, not any similarly-numbered document. I have not auto-corrected or substituted any other number.

1. The patent under review (verified)

Claims at issue: 1–3 (fiber), 4–11 (spinning process), 12–15 (liquid crystalline solution). Independent claim 1 requires (a) a polymer of hexose units, (b) ≥50% of the hexose units linked by α(1→3) glycoside linkage, (c) number-average DP ≥100, and (d) fiber tensile strength ≥1 g/denier. Independent claim 4 requires a liquid crystalline dope at ≥20% solids; claim 12 is the corresponding solution claim.

Source caution: The Google Patents text supplied in the prompt displays the "Cited By" (forward-citation) list — 208 entries — which is not prior art. Most of those entries (a "Stator," a "surgical clip advancement mechanism," "variable capacitor arrays," etc.) are third-party noise and are irrelevant to §102. The relevant material is the "References Cited" block on the face of the patent, which I retrieved separately. Since this is a pre-AIA case (priority 25 Jan 1999, filed 19 Jan 2000), §102(a)/(b)/(e) as they read at that time govern.

2. References cited on the face of US 7,000,000

Per the patent's "Referenced Cited" listing (patents.justia.com/patent/7000000):

U.S. patent documents

1. US 4,072,567 — Yokobayashi et al. — 7 Feb 1978
2. US 4,109,663 — Maeda et al. — 29 Aug 1978
3. US 4,306,059 — Yokobayashi et al. — 15 Dec 1981
4. US 4,501,886 — O'Brien — 26 Feb 1985
5. US 4,830,752 — Shibata et al. — 16 May 1989

Foreign patent documents
6. WO 96/06173 — Feb 1996
7. WO 99/40217 — Aug 1999

Non-patent literature
8. Simpson et al., Microbiology, vol. 141, pp. 1451–1460 (1995)
9. Ogawa et al., Fiber Diffraction Methods, 47, pp. 353–362 (1980)
10. Applied Fibre Science, F. Happey, Ed., Ch. 8 (E. Atkins), Academic Press, New York, 1979

3. Reference-by-reference analysis

3.1 US 4,306,059 — Yokobayashi et al. ("Shaped products of alpha-glucan"), granted 15 Dec 1981

• Dates: Filed 25 Sep 1978 (Ser. 05/945,129); JP priority 29/30 Sep 1977; granted 15 Dec 1981. Pre-1999 by >17 years → §102(b).
• Disclosure (verified): Shaped bodies — expressly including "filament, fiber, thread, stick, rod, rope, net, cloth, gauze, film…" — made from "elsinan," an alpha-glucan of MW 10,000–10,000,000 built of repeating units [3)-Glc-(1→4)-Glc-(1→4)-Glc-(1→], i.e., ~68% α(1→4) and only ~30% α(1→3) linkages (methylation data: 2,4,6-tri-O-methyl-D-glucose ≈30% [1,3-linked]; 2,3,6-tri-O-methyl-D-glucose ≈68% [1,4-linked]).
• §102 mapping: This is the closest structural prior art — a pre-existing alpha-glucan fiber. But the α(1→3) content is only ~30%, below the "at least 50%" threshold that is a positive limitation of claims 1, 4 and 12 and of dependent claims 2, 5, 13 ("substantially all" = ≥90%). Consequently it does not anticipate any claim of US 7,000,000 under §102, because it fails the ≥50% α(1→3) limitation (and discloses no liquid-crystalline dope at ≥20% solids and no ≥1 g/denier value). Its real force is as §103 art, especially in combination with refs 8 and 9.
• Claim-by-claim: no §102 anticipation of claims 1–15; potentially §103 against claims 1, 3, 6, 7, 9, 10 to the extent those generic features (fiber from an α-linked glucan; acetylation/deacetylation) are disclosed.

3.2 US 4,501,886 — O'Brien ("Cellulosic fibers from anisotropic solutions"), granted 26 Feb 1985

• Dates: Filed 9 Aug 1982; granted 26 Feb 1985 → §102(b). Same inventor, so also of interest as the patent's own admitted starting point.
• Disclosure: Spinning of cellulose (β(1→4) glucan) fibers from anisotropic/liquid-crystalline dopes; it is the reference the specification cites for both "cellulose forms liquid crystalline solutions" and "spinning from the liquid crystalline solution can be accomplished by means known in the art, and as described in O'Brien."
• §102 mapping: This reference supplies the generic process architecture of claims 4–15 (dissolve polymer → liquid crystalline dope → extrude through spinneret → coagulate → optionally draw/regenerate) but its polymer is not an α(1→3)-linked hexose polymer. It therefore cannot anticipate any of claims 4–15, each of which includes the α(1→3) polymer limitation, nor claims 1–3. It is available as §102(a)/§103 background art and, in combination with refs 8/9, is the most likely vehicle for a §103 attack on claims 4, 10, 11, 12, 15. Note also that the specification's statement that prior art taught chain extension only in β(1→4) polysaccharides is an admission against the obviousness of the α(1→3) species.

3.3 US 4,072,567 — Yokobayashi et al., granted 7 Feb 1978

• Dates: Granted 7 Feb 1978 → §102(b). (I could not verify the filing date from the sources retrieved.)
• Disclosure: Listed on the face of US 4,306,059 as "Compound water-insoluble glucan and process for the production thereof." It is a fermentation-derived, water-insoluble glucan (same inventorship family as ref 3.1), i.e., a biologically produced polyglucan.
• §102 mapping: On its face it is directed to a polymer/method, not to a fiber, and I have not verified that the glucan it produces has ≥50% α(1→3) linkages or a DP ≥100 as an oriented fiber. Treat as potential §102 art only against the polymer component of claim 1 (and possibly claim 3 if the glucan is α(1→3)-D-glucan); absent verification it should be treated as §103 background. ⚠️ Verification needed — I am flagging this rather than guessing.

3.4 US 4,109,663 — Maeda et al., granted 29 Aug 1978

• Dates: Granted 29 Aug 1978 → §102(b).
• Disclosure: ⚠️ I could not confirm the subject matter of this reference from the material retrieved in this session. It is listed among the glucan/polysaccharide citations on the face of US 7,000,000.
• §102 mapping: Because its disclosure is unverified, I cannot responsibly assign it a claim-specific anticipation position. If it is a polysaccharide-shaping or glucan-production reference, its ceiling would be §102 against the polymer element of claim 1 or §103 against the process claims. Recommend retrieving the document before relying on it.

3.5 US 4,830,752 — Shibata et al., granted 16 May 1989

• Dates: Granted 16 May 1989 → §102(b).
• Disclosure: ⚠️ Subject matter not verified in this session. It appears in the citation set alongside the glucan/α-glucan shaping art.
• §102 mapping: Unverified; no claim-specific anticipation can be asserted. Recommend retrieval.

3.6 WO 96/06173 — published February 1996

• Dates: Published Feb 1996 → more than one year before the 25 Jan 1999 priority date, so a §102(b) printed publication.
• Disclosure: ⚠️ Not verified in this session. Given its position among the cited documents it is presumably a glucan/polysaccharide molding or shaping publication.
• §102 mapping: Cannot be assigned to specific claims without verification. Recommend retrieval.

3.7 WO 99/40217 — published August 1999

• Dates: Published Aug 1999 — after the 25 Jan 1999 priority date, and after the 19 Jan 2000 filing it is only "later-published." It is therefore not available under §102(a) or §102(b).
• §102(e) caveat: It could have §102(e) effect only if it is a PCT designating the United States and published in English, in which case it is prior art as of its international filing date. For international applications filed before 29 Nov 2000, English-language publication was required for §102(e) effect. If (as I suspect but could not confirm) this document published in Japanese, it carries no §102(e) date and is effectively not prior art to US 7,000,000. Its presence on the face of the patent is therefore probably as an "art of interest" citation, not as an anticipation reference.
• §102 mapping: No anticipation of any claim unless the English-publication/§102(e) predicate can be established.

3.8 Simpson et al., Microbiology 141:1451–1460 (1995)

• Date: 1995 → §102(b).
• Disclosure (verified): Isolation of the α(1→3) glucan polymer by contacting aqueous sucrose with GtfJ glucosyltransferase from Streptococcus salivarius. This is the reference the patent itself cites as the source of its polymer (the specification's "Polymer Isolation" section clones gtf-J using primers based on GenBank Z11873 and on Giggard et al. 1991).
• §102 mapping: This is the single most dangerous §102 reference against claim 1's polymer element — it discloses an α(1→3) glucan of the claimed enchainment pattern. However it discloses no fiber, no tensile strength, and no liquid-crystalline solution. It therefore does not anticipate claims 1, 4 or 12 (each has at least one limitation absent from Simpson). It is the natural §103 partner for refs 3.1/3.2 to attack claims 1–15, and it independently anticipates nothing.
• Note: because this is a printed publication from 1995, it also defeats any argument that the α(1→3) glucan itself was novel as a composition.

3.9 Ogawa et al., Fiber Diffraction Methods 47:353–362 (1980)

• Date: 1980 → §102(b).
• Disclosure (verified via the patent's own characterisation and the related literature): Highly crystalline, highly oriented, low molecular weight films of α(1→3)-D-glucan: the insoluble glucan is acetylated, dissolved at 5% in chloroform, cast into a film, stretched 6.5× in glycerine at 150 °C, then deacetylated and crystallised by annealing in superheated water at 140 °C.
• §102 mapping: Discloses the α(1→3)-D-glucan, its acetylation (claim 7), the poly(α(1→3)-D-glucose) acetate species (claim 8) and the regeneration/deacetylation step (claim 9) — but only in the context of a film, from a non-liquid-crystalline 5% solution. It discloses no liquid crystalline solution, no ≥20% solids dope, no fiber, and no tensile property. It therefore cannot anticipate claims 1–15 as a whole; every one of claims 4–11 and 12–15 contains the "liquid crystalline solution" limitation that Ogawa's 5% chloroform casting does not meet, and claims 1–3 contain the fiber/tensile limitations. Strong §103 reference; it is the reference that most nearly bridges the gap between the polymer (ref 3.8) and a shaped, oriented article.
• The same group's related papers (Carbohydr. Res. 75 (1979) C13–C16, "X-ray diffraction data for (1→3)-α-D-glucan"; Int. J. Biol. Macromol. 3 (1981) 31–36; Carbohydr. Polym. 3 (1983) 287–297, "X-ray diffraction data for (1→3)-α-D-glucan triacetate") are not on the face of US 7,000,000 but were expressly used in later EPO oppositions against DuPont's follow-on α-1,3-glucan cases — see the EPO search report on PCT/US2015/037634 (WO 2015/200596 family), which cites all four Ogawa papers as X art with the "Y" art being the 1983 triacetate paper.

3.10 Applied Fibre Science, F. Happey Ed., Ch. 8 (E. Atkins), Academic Press, New York, 1979

• Date: 1979 → §102(b).
• Disclosure: General treatise chapter on polysaccharide fibre science and cellulose; the background cited by the specification for "polysaccharides have been known since the dawn of civilization" and for the crystallography of the α(1→3)-D-glucan backbone.
• §102 mapping: No anticipation of any claim — it is a general background/state-of-the-art citation (§102(a) "art of interest"). Its only role is to establish that the extended-helix structure of α(1→3)-D-glucan was known, which cuts against non-obviousness of the "α(1→3) polysaccharides can form liquid crystals" discovery asserted in the specification.

4. Overall §102 conclusion

Bottom line: No reference cited on the face of US 7,000,000 anticipates any of claims 1–15 under §102, because each independent claim contains a limitation absent from every reference:

• claim 1: ≥50% α(1→3)-linked hexose units and fiber form and ≥1 g/denier;
• claim 4: formation of a liquid crystalline solution at ≥20% solids from an α(1→3) polymer;
• claim 12: the liquid crystalline solution itself at ≥20% solids.

The patent's actual novelty rests on the discovery that the α(1→3) backbone is sufficiently chain-extended to form a lyotropic liquid crystalline phase — a proposition the specification itself says the prior art (ref 3.2 and ref 3.10) taught against ("sufficient polysaccharide chain extension could be achieved only in β(1→4) linked polysaccharides… any significant deviation… would lower the molecular aspect ratio below that required for the formation of an ordered phase"). Anticipation therefore fails; the realistic invalidity theory is a §103 combination of Simpson 1995 (the α(1→3) glucan) + Ogawa 1980 (acetylation, film, orientation, deacetylation) + Yokobayashi 4,306,059 and/or O'Brien 4,501,886 (fibre spinning from α-glucan / from anisotropic dopes) — with the "teaching away" statement in the specification being the patentee's principal rebuttal.

5. Explicit limitations of this analysis

1. I did not open the USPTO PatentCenter/Patent Application Image File (the printed "References Cited" front page) directly; the reference list was taken from the patent's Justia record, which reproduces that block verbatim (including examiners, art unit class, and the three NPL items). The same three NPL items are independently confirmed in the WO 2013/036918 A2 citation record ("E. ATKINS: Applied Fiber Science 1979; OGAWA ET AL., Fiber Diffraction Methods, vol. 47, 1980, pp. 353–362; SIMPSON ET AL., Microbiology, vol. 141, 1995, pp. 1451–1460").
2. I was unable to verify the disclosure content of US 4,072,567, US 4,109,663, US 4,830,752 and WO 96/06173 within this session. I have flagged those rather than guessing; each should be pulled in full before any §102 position is asserted against a specific claim.
3. The §102(e)/language-publication point on WO 99/40217 is stated as a legal predicate to be checked against the document itself, not as a verified fact.
4. Everything above reflects the "current ground truth" as of the retrieval date; if any later source contradicts it, the later source should govern.

I'll ground this analysis by checking the key prior-art references identified on the page (O'Brien, Simpson et al., Ogawa et al.), since the page's "Cited By" list is mostly forward citations that post-date the 1999 priority date and therefore cannot be § 102/§ 103 prior art.

Obviousness Analysis — US 7,000,000 B1 ("Polysaccharide fibers," O'Brien)

Prepared for: Technical patent analysis
Patent: US 7,000,000 B1 (US 09/857,572); priority 1999‑01‑25; filed 2000‑01‑19; granted 2006‑02‑14; inventor John P. O'Brien; original assignee E. I. du Pont de Nemours & Co.
Statute applied: 35 U.S.C. § 103(a) (pre‑AIA, critical date 1999‑01‑25)
Note on dates: The system date shown to me (2026‑09‑18) and the date in your prompt (2026‑04‑26) conflict; I flagged this and did not rely on either for the legal analysis.

1. What on this page actually constitutes prior art

A threshold caution: the "Cited By (208)" table on the Google Patents page is forward citation data — i.e., later documents that cite US 7,000,000. Almost all of those entries post‑date the 1999‑01‑25 critical date (DuPont's own 2011–2016 family such as WO 2013/052730, US 9,175,423, US 9,336,584; Lenzing's 2013–2014 family; Procter & Gamble fibrous structures; etc.). Those are not § 102/§ 103 prior art against this patent and cannot be combined in an obviousness rejection. A few "Cited By" records backdate to 1997–2000, but they are unrelated electromechanical/camera art and are non‑analogous.

The genuinely citable prior art disclosed within the patent's own Background and Detailed Description is:

Only (A), (B), (C), (D), (E) and (F) are usable. All are printed publications more than one year before 1999‑01‑25, so all qualify under pre‑AIA § 102(b) and may be combined under § 103(a).

No single reference anticipates. Ogawa (C) never forms a liquid crystalline dope (his only successful article is an isotropic 5% chloroform cast film) and makes no fiber; O'Brien (A) is directed to cellulose (β(1→4)), not α(1→3) glucan; Simpson (B) discloses a polymer and enzyme, not a fiber. So the case rises or falls on § 103 combinations.

2. Person having ordinary skill in the art (PHOSITA) and claim construction

PHOSITA: a polymer/chemical engineer or fiber scientist with an advanced degree (or equivalent experience) and 3–5 years in solution spinning of cellulose and cellulose derivatives, familiar with lyotropic (anisotropic) "dope" spinning, esterification of polysaccharides, and the X‑ray/polarized‑light characterizations that confirm oriented phases.

Key claim limitations to map against the art:

• Claims 1–3: fiber; polymer with ≥50% (claim 2: "substantially all," spec = ≥90%) α(1→3) hexose linkages; number‑average DP ≥ 100; tensile strength ≥ 1 g/denier (spec ¶ "tensile strength of at least 1 gram per denier, preferably 2").
• Claim 4: process — dissolve such polymer to form a liquid crystalline solution having solids content ≥ 20%, then spin.
• Claims 5–9: ≥90% α(1→3); derivatization; acetylation; poly(α(1→3)‑D‑glucose acetate); saponification/hydrolysis to regenerate.
• Claim 10: solvent = organic acid / organic halide / fluorinated alcohol / mixtures.
• Claim 11: solids 20–35%.
• Claims 12–15: the liquid crystalline solution per se, solids ≥ 20%, corresponding dependent features.

Note a drafting point worth flagging: the claims require ≥20% solids, whereas the specification states the preferred floor as "at least 10%." The claims therefore sit at the high‑solids end of the disclosure — which is exactly the region O'Brien (A) teaches for cellulose triacetate (see § 4).

3. The single most damaging combination: Ogawa (C) + O'Brien (A)

This is the combination an examiner or a validity challenger would lead with.

What each reference contributes

• (C) Ogawa supplies every α(1→3)‑glucan‑specific teaching: the polymer is (1→3)‑α‑D‑glucan; it has an extended, ribbon‑like backbone "similar to cellulose"; it can be acetylated; the acetate is soluble and film‑forming in an organic solvent (chloroform); the cast article can be drawn/oriented; and deacetylation regenerates the glucan. Ogawa even states that chain conformation should be understood in terms paralleling cellulose.
• (A) O'Brien supplies the entire fiber toolkit for polysaccharide acetates: forming optically anisotropic (liquid crystalline) high‑solids dopes (30–42 wt% cellulose triacetate; TFA/H₂O ≈ 35–42 wt% solids, TFA/CH₂Cl₂ molar‑ratio window giving "35 to 42% solids"), air‑gap spinning through an inert non‑coagulating layer into a 1–3 carbon alcohol (methanol) bath, acetylation via acetic anhydride/glacial acetic acid/methylene chloride with perchloric acid catalyst, and saponification under tension to regenerated fiber — all of which reappear, almost element‑for‑element, in US 7,000,000 (compare claim 9 "saponification or hydrolysis medium," claim 10 solvent class, and Example 1's TFA/H₂O 100/8 and TFA/CH₂Cl₂ 60/40 dopes and 0.05 M methanolic sodium methoxide deacetylation). The O'Brien disclosure text is confirmed in the search results at sumobrain (air‑gap spinning, TFA, methanol bath, 30–42% solids, saponification, ASTM D2101 testing) and reproduced in the DuPont EP 0103398 counterpart.

The motivation to combine (why a PHOSITA would do it)

1. Same problem, same class of material. The opening paragraphs of (A) explicitly frame the goal as high‑tenacity fibers "from renewable sources, such as the cellulosics" and note that "anisotropic solutions provide the opportunity for spinning at high concentrations without excessive viscosities." Ogawa explicitly analogizes (1→3)‑α‑D‑glucan to cellulose. A PHOSITA seeking a new renewable, cellulosic‑like fiber would naturally take the newly characterized α(1→3) glucan and run it through the known cellulose‑triacetate anisotropic spinning process.
2. Ogawa hands over the enabling chemistry (acetylation + organic‑solvent solubility). The reason to acetylate — to reach a solids level sufficient for a lyotropic phase — is precisely what (A) teaches ("adequate solvents for forming high concentration solutions … have not been available" → derivatize). Ogawa proves the α(1→3) glucan acetate is soluble in an organic solvent; (A) teaches which solvents (TFA/CH₂Cl₂, TFA/H₂O) form anisotropic phases.
3. The numerical limitations are already in (A). Claims 4, 11 and 12 require "at least 20%" and "20 to about 35%" solids. O'Brien teaches anisotropic dopes at 30–42 wt% and specifically calls out 35–42% solids for optimum spinnability — i.e., the claimed range is a subset of the range taught for the analogous polymer acetate. Under In re Woodruff / In re Peterson, a claimed numerical range embraced by, or closely adjacent to, a prior‑art range is prima facie obvious absent a demonstrated criticality.
4. Claim 10/15 solvent recitation is verbatim O'Brien. "organic acid … organic halide … fluorinated alcohol … mixtures" = TFA, methylene chloride, hexafluoroisopropanol — all named in (A).
5. Claim 9 regeneration is verbatim O'Brien (saponified, high‑tenacity regenerated cellulose fibers; the patent even adopts the same 0.05 M sodium‑methoxide‑in‑methanol saponification used in (A)).

Reasonable expectation of success. Because (A) teaches that the acetate of an extended‑chain polyglucose forms a lyotropic dope and spins to a highly oriented fiber, and (C) teaches that the (1→3)‑α‑D‑glucan backbone is also extended/ribbon‑like and can be acetylated, a PHOSITA would have had a reasonable expectation that the acetylated α(1→3) glucan would behave analogously to cellulose triacetate — i.e., "obvious to try" with a reasonable expectation of success under KSR v. Teleflex.

4. The full three‑reference combination: Ogawa (C) + O'Brien (A) + Simpson (B)

Adding Simpson (B) closes the remaining gap — material supply and linkage purity — and strengthens the motivation.

• (B) discloses that a single, cloned enzyme (GtfJ) produces an insoluble glucan "composed mainly of α‑(1→3)‑linked glucosyl residues," i.e., a practical, scalable route to the very polymer that (C) had to obtain by Smith degradation and that (A) teaches how to spin. (B) therefore supplies both the "substantially all α(1→3)" teaching of claims 2/5/13 and the poly(α(1→3)‑D‑glucose) identity of claims 3/8 (with acetylation per (C)/(A)).
• (B) is the art‑recognized enabling reference for the S. salivarius enzyme; the patent itself cites (B) at column 1 as the source of the glucan, and later DuPont filings describe (B) as the source of the wild‑type gtfJ used to make the fiber polymer (see US 9,169,506).
• Motivation: a PHOSITA wanting commercial quantities of an α(1→3) glucan substrate for the (A)/(C) process would look directly to (B)/(D), which teach how to make it recombinantly and how to select the correct enzyme (GtfJ) that yields the α(1→3)‑rich, water‑insoluble glucan (which is also advantageous — an insoluble polymer is easy to isolate).

Ancillary references. Aspinall (F) supplies the catalogue of polysaccharide derivatives (acetate, nitrate, methyl/ethyl/hydroxyethyl, propionate, butyrate) recited in the specification and reinforces that esterification is routine for rendering polysaccharides soluble; Happey/Atkins (E) is generic fiber‑science background. Neither is necessary to the rejection but both support "routine choice of known derivatives."

5. Claim‑by‑claim obviousness posture

The weakest link in the prima facie case is claim 1's requirement that the α(1→3) glucan actually form a spinnable, high‑strength fiber, because the α(1→3) material's DP/tensile properties are not demonstrated in (C) (Ogawa explicitly calls his sample "low molecular weight," [η] = 0.52 dL/g, and he obtained only a film, not a fiber).

6. The counter‑case: why the claims arguably survive (teaching‑away + unexpected results)

The strongest nonobviousness positions are built on the art's own statements:

1. Express teaching away from α‑linked ordered phases. The patent's Background (and O'Brien's own patents) states: "the teachings of the art suggest that sufficient polysaccharide chain extension could be achieved only in β(1→4) linked polysaccharides and that any significant deviation from that backbone geometry would lower the molecular aspect ratio below that required for the formation of an ordered phase." If accepted as the state of the art, this is a classic In re Gurley / DePuy‑style teaching away from expecting α(1→3) glucan to form a lyotropic phase at all. That is the crux of the allowance.

2. Ogawa's documented failures cut directly against the combination. Ogawa reports that a continuous film or fiber could not be made from (1→3)‑α‑D‑glucan solutions in aqueous alkali, hydrazine hydrate, or NMMO/DMSO — and that success required abandoning solution spinning altogether for a low‑solids (5%) chloroform cast film plus 150 °C glycerine stretch and 140 °C aqueous anneal. The patent expressly notes that such hot aqueous treatment causes chain cleavage/MW loss. So (C) arguably teaches away from the (A) route and provides no suggestion that a ≥20%‑solids anisotropic dope is attainable.

3. Unexpected results. The specification presents the property that α(1→3) glucan (and mixed α(1→3)/α(1→4) glucans such as nigeran) form liquid crystalline solutions, while α(1→4) (amylose), α(1→6) (dextran) and α(1→4)/α(1→6) (pullulan) do not (Examples 1, 7; Comparative Examples 3–4). The Examples report as‑spun α(1→3) fibers at 4.2 g/den tenacity / 17.5% elongation / 53.9 g/den modulus (Example 1) and regenerated fibers at 2.4–2.7 g/den — far above the 1 g/den claim floor and markedly better than the α(1→4) control. If proffered with a nexus, this supports nonobviousness under In re Soni / WBIP.

4. Material difference: DP and MW. Ogawa's glucan is low‑MW; a PHOSITA following (C) would not necessarily arrive at a polymer meeting claim 1's DP ≥ 100 and spin‑stretch continuity. The patent's own answer — producing higher‑MW polymer via the GtfJ route with Mn ≈ 60,800 (Example 1) — is a real difference over (C).

5. Claim‑construction/§ 112 wrinkle. Because the claims require ≥20% solids while the specification frames ≥10% as the operative floor, the applicant may have difficulty showing that the claimed range (as opposed to 10%) is critical — which weakens the "criticality" rebuttal to the Woodruff/Peterson range‑obviousness point on claims 4/11/12.

Net: a court or examiner applying KSR could well find claims 4, 6–12 and 15 obvious over Ogawa + O'Brien (+ Simpson), while claims 1–3, 13–14 are more defensible on the strength of (i) the art's β‑only teaching‑away and (ii) the unexpected lyotropic behavior of α(1→3) glucan.

7. Bottom line

• No anticipation by any single reference on this page.
• The primary § 103(a) combination is Ogawa (1980) + O'Brien U.S. 4,501,886 (1985), optionally with Simpson et al. (1995) and the Giffard (1991)/GenBank Z11873 material for the enzyme route. Ogawa supplies the α(1→3) glucan, its cellulose‑analogous extended backbone, and acetylation/solubility; O'Brien supplies the lyotropic high‑solids spinning process, the solvent systems, the acetylation/coagulation/saponification sequence, and the >20% solids figures; Simpson supplies the scalable α(1→3)‑rich polymer.
• The motivation to combine is strong (same technical field, same "high‑tenacity fiber from renewable polysaccharide" objective, express cellulose analogy in Ogawa, and the numeric ranges already disclosed in O'Brien).
• The best nonobviousness defenses are (1) the art's express statement that only β(1→4) backbones provide sufficient chain extension for an ordered phase, and (2) Ogawa's own failed attempts at α(1→3) glucan solution spinning plus the unexpected lyotropic behavior and the 4.2 g/den fiber results. These are what presumably carried the claims to allowance.
• Caveat on the record: The 200‑plus "Cited By" entries are forward citations and are not prior art here; do not use them in a § 103 rejection. Any use of DuPont's own later filings (e.g., WO 2013/052730) is limited to showing how the applicant characterized US 7,000,000 — not as evidence of obviousness, since those documents post‑date the critical date.

Confidence notes: I have high confidence in the identities/dates of O'Brien 4,501,886, Simpson 1995, and Ogawa 1980 as prior art and in their general teachings (confirmed via the sources linked above). I am less certain of Ogawa's exact molecular weight/DP relative to claim 1's "DP ≥ 100" floor — the search results confirm only that Ogawa's sample was low‑MW and yielded a film, not a fiber — so I would verify Ogawa's reported DP directly from the primary text before relying on that point in a formal rejection.