Gellan Gum Fermentation Patent Revoked by the EPO: What the 2026 Decision Means

A recent European patent decision provides an interesting look at the technology behind gellan gum fermentation.

On February 24, 2026, the European Patent Office (EPO) Board of Appeal issued its decision in case T 0548/24, concerning European patent EP 3 483 280, titled “A fermentation method for producing gellan gum.”

The Board of Appeal set aside the previous decision and ordered:

> “The patent is revoked.”

The central legal issue was inventive step under Article 56 of the European Patent Convention (EPC).

Source: EPO Board of Appeal — T 0548/24

What Was the Patent About?

Gellan gum is a microbial polysaccharide produced through fermentation, commonly associated with microorganisms such as Sphingomonas species.

Traditional microbial production generally involves preparing a seed culture before transferring it into a production fermenter.

The patent examined in this case proposed a different approach: part of a previous fermentation broth could be used as the inoculum for the next fermentation.

In simplified form:

Conventional process:

Microbial strain → Seed cultivation → Production fermentation → Gellan gum recovery

Proposed process:

Previous fermentation → Part of fermentation broth retained → Used as inoculum → Next fermentation

The patent's independent claim specified using 3–50% of the fermentation broth as the seed for a subsequent fermentation, without separating the cells from the fermentation broth.

The complete claims and technical disclosure are available in the original European patent publication:

Source: EP 3 483 280 B1 — European Patent Office

Why Is Seed Preparation Important?

In microbial fermentation, seed preparation is an important part of the production process. A culture must generally be developed to a suitable physiological state before it is transferred into the production fermenter.

This can require:

• Separate seed vessels
• Additional culture medium
• Sterilization
• Transfer operations
• Aseptic handling
• Additional process time
• Additional equipment

The patent specification discussed these considerations and proposed using part of an existing fermentation broth to simplify the seed preparation stage.

For a large-scale fermentation process, reducing the number of seed preparation steps can potentially affect equipment utilization and production workflow.

Source: EP 3 483 280 B1 — European Patent Office

What Did the Patent Actually Demonstrate?

The patent included experimental examples in which fermentation broth from one production round was used to initiate another fermentation round.

For example, in one experiment, 375 g of fermentation broth from the first fermentation round was transferred into a fermenter containing 7.5 L of sterilized fermentation medium. The second fermentation was then carried out under the described conditions.

The patent reported fermentation times of 48 hours for both rounds. The reported gellan gum contents were 5.22 g/kg in Round 1 and 5.10 g/kg in Round 2.

These experimental details are important because they show that the patent included experimental data concerning repeated fermentation rather than describing the concept only theoretically.

Source: EP 3 483 280 B1 — European Patent Office

Why Did the Patent Become a Patentability Issue?

The important distinction is between technical usefulness and patentable inventiveness.

A process can work in practice and still fail to satisfy the inventive-step requirement of patent law.

For a European patent, the question is not simply whether an earlier document contains exactly the same wording as the later claim.

Under Article 56 EPC, the question is whether the claimed solution would have been obvious to a person skilled in the relevant technical field, taking the prior art and common general knowledge into account.

In this case, the Board of Appeal considered earlier disclosures concerning fermentation and the use of culture material from one fermentation as inoculum for another.

The key question therefore became whether applying this fermentation strategy to gellan gum involved an inventive technical contribution.

The Board ultimately concluded that the claimed subject matter did not involve an inventive step.

Sources: EPO Board of Appeal — T 0548/24 · EPO — Article 56 EPC

Earlier Fermentation Knowledge Was Important

One of the prior-art documents considered in the proceedings described fermentation of exopolysaccharides using microorganisms including Sphingomonas.

It also discussed semi-batch fermentation and the use of material from one fermentation as inoculum for another.

This was relevant because gellan gum is itself a microbial exopolysaccharide.

The Board therefore considered whether a skilled person starting from the earlier technology would have been motivated to apply the same general fermentation concept to gellan gum production.

The Board ultimately concluded that the claimed process did not involve an inventive step.

Source: EPO Board of Appeal — T 0548/24

What About the 3–50% Range?

The claimed range of 3–50% fermentation broth is one of the most interesting technical details of the case.

A numerical range can sometimes provide a meaningful distinction from earlier technology. However, a numerical range does not automatically establish inventive step.

The relevant question is whether the selected range produces an unexpected technical effect or otherwise represents a non-obvious technical contribution.

The appeal proceedings considered earlier fermentation knowledge involving the transfer of a portion of an existing culture into a subsequent fermentation.

The Board concluded that the claimed range did not provide sufficient inventive distinction from the prior art and common general knowledge.

Source: EPO Board of Appeal — T 0548/24

The Special Challenge of Gellan Gum Fermentation

Gellan gum fermentation has an important characteristic that makes the process technically interesting: broth viscosity can increase as polysaccharide is produced.

Increasing viscosity can affect:

• Mixing
• Oxygen transfer
• Mass transfer
• Fermentation control
• Heat transfer

These characteristics could make the direct reuse of fermentation broth appear less straightforward than ordinary microbial seed transfer.

Arguments concerning the particular characteristics of gellan gum fermentation were considered during the appeal. However, the Board did not consider these issues sufficient to establish an inventive step for the claimed process.

Source: EPO Board of Appeal — T 0548/24

A Key Lesson: Technical Effects Need Evidence

The case also illustrates an important principle in process patents.

A new fermentation process may be described as providing advantages such as:

• Simplified production
• Reduced seed preparation
• Shorter processing time
• Lower contamination risk
• Improved productivity
• Lower production cost

However, when an unexpected technical effect is relied upon to establish inventive step, experimental evidence demonstrating that effect can become important.

For fermentation technology, useful comparisons may include:

Parameter	Conventional Process	Proposed Process
Fermentation time	Measured value	Measured value
Gellan gum yield	Measured value	Measured value
Productivity	Measured value	Measured value
Biomass development	Measured value	Measured value
Broth viscosity	Measured value	Measured value
Seed preparation time	Measured value	Measured value

Comparative data can help establish whether a process provides an unexpected technical advantage rather than simply applying a known fermentation principle in a new context.

Patent Revocation Does Not Mean the Process Does Not Work

This distinction is important.

The EPO decision did not determine that the fermentation method was technically impossible or that the process could not produce gellan gum.

The legal issue was whether the claimed subject matter satisfied the requirements for patent protection.

The Board concluded that the claimed subject matter lacked the required inventive step and therefore revoked the patent.

In simple terms:

> Patent revoked ≠ technology does not work.

Rather:

> Patent revoked = the European patent could not be maintained because the claimed invention did not meet the inventive-step requirement.

Source: EPO Board of Appeal — T 0548/24

What Does This Tell Us About Gellan Gum Technology?

The case illustrates how much gellan gum manufacturing depends on established fermentation science.

The final gellan gum powder is only the visible end product. Behind it are several stages of biotechnology and process engineering:

Microbial strain → Medium preparation → Seed cultivation → Fermentation → Polysaccharide production → Recovery → Purification → Drying → Gellan gum

Each stage can potentially become an area of process development or intellectual-property research.

Potential areas of technical development include:

• Microbial strain selection
• Culture conditions
• Carbon and nitrogen sources
• Seed preparation
• Inoculum management
• Oxygen transfer
• pH control
• Fermentation temperature
• Feeding strategies
• Fermentation time
• Downstream recovery
• Product purification

At the same time, many individual fermentation concepts have been known for decades.

This creates an important challenge for process patents:

> Is the claimed process genuinely inventive, or is it an application of established fermentation knowledge to a particular microorganism or product?

The 2026 EPO decision provides a useful real-world example of how that question can determine whether a gellan gum manufacturing patent survives opposition and appeal proceedings.

Why This Case Matters Beyond One Patent

Gellan gum is a specialized hydrocolloid, but its production is based on sophisticated microbial fermentation.

The case demonstrates that innovation in gellan gum does not necessarily have to involve a new chemical structure or a new application. Manufacturing efficiency itself can be an important area of research.

However, process innovations also need to be considered carefully against existing fermentation knowledge.

A seemingly simple change—such as reusing part of a previous fermentation as inoculum—may already have analogues in other fermentation systems.

For this reason, patent research in gellan gum should look beyond documents that specifically mention “gellan gum.” Relevant prior art may also come from broader fields such as microbial fermentation, exopolysaccharide production, semi-batch fermentation and inoculum preparation.

Official References

• EPO Board of Appeal — T 0548/24 — Final decision concerning EP 3 483 280.
• EP 3 483 280 B1 — EPO Publication Server — Original European patent specification, including claims and experimental examples.
• European Patent Register — Official EPO database for European patent procedural and legal-status information.
• EPO Espacenet — EPO patent search database.
• EPO — Article 56 EPC: Inventive step — Legal basis for the inventive-step requirement.

Gellan Gum Supplier Reference

For commercial High Acyl Gellan Gum and Low Acyl Gellan Gum (E418), CINOGEL BIOTECH supplies gellan gum for food, beverage, plant-based products, bakery, confectionery and plant tissue culture applications.

Product information is available at:

CINOGEL BIOTECH — Gellan Gum Products

This article is provided for technical and informational purposes. It is not legal advice or a legal opinion concerning the validity or enforceability of any patent.