The assignee ranking covers 100 companies drawn from the 546 records in scope, and it is concentrated at the top: the leading assignee holds 40 records, and the top 5 combined account for 30.0% of all 546 records. That leaves a long tail of smaller filers and single-record entrants below the top 10, which together hold 48.4% of the field. Anyone doing freedom-to-operate work should focus first on the leaders rather than the tail, since claim density is heaviest there.

Filings peaked at 26 records in 2020 and fell to 5 by 2024, a 67% decline over that three-year span. However, because patent publication typically lags filing by around 18 months, the 2025 and 2026 figures in this dataset are still incomplete and cannot yet be read as confirmation of a continued slowdown. The safest reading is that activity cooled from its 2020 peak, without drawing conclusions about the most recent one to two years.

D21C, covering pulp production and treatment, appears in 61.5% of the 546 records and is the largest single classification. C12N, covering microorganisms and genetic engineering, follows at 36.4%, reflecting how much of the field's activity is upstream enzyme development rather than the bleaching step itself. Dedicated bleaching and dry-cleaning claims under D06L are comparatively narrow at 6.2%, which is useful context if you assumed bleaching-specific claims were the field's centre of gravity.

US10718088B2, assigned to Enzymatic Deinking Technologies, covers enzymatic pre-treatment of market pulp applied before wetlapping, drying or repulping, aimed at improving fibre drainage and strength in the final paper product. Its scope is tied to that specific process timing and outcome, so work that applies enzymes at a different process stage or targets a different property, such as brightness, likely falls outside its literal claims. It remains a useful reference point for anyone building a deinking or fibre-recovery process to check against.

The thinnest branches relative to the 546-record total are C11D detergent and cleaning compositions at 7.5%, C12R microorganism indexing at 6.4%, and D06L bleaching-specific claims at 6.2%, all far below the D21C pulp-treatment core at 61.5%. Only 10 co-assignee pairs appear across the entire dataset, indicating limited cross-institution collaboration outside a small cluster. A specific combination claim tying an enzyme class to a defined detergent carrier at a stated bleaching stage is one plausible way to file into that space without colliding with the dense pulp-treatment prior art.