Rhamnolipids: Structure, Properties, Production and Applications

In short

“Rhamnolipid” names a family, not a product. A grade may be one defined congener, a congener-enriched mixture, or a fermentation product carrying water, salts and residual components as well.

A CAS number that belongs to one defined congener does not identify a commercial mixture. PubChem's mono-rhamnolipid record is one molecule; a grade is identified by its own composition statement and regulatory documents.

Active content is not purity. Total solids, total glycolipids and total rhamnolipids are different measurements, and a percentage says nothing until the method and the calculation basis are stated.

Purification is a cost decision, not a quality ranking. The target is reproducible quality for the intended formulation, not the highest number available.

Cleaning is where the commercial evidence is clearest. Research interest in remediation, oilfield, food and pharmaceutical uses is not the same thing as grade-specific commercial approval.

Select on the application, not on the name. Rhamnolipids should be compared as application-specific products rather than by product name, CAS number or headline purity.

Rhamnolipids are fermentation-derived glycolipid biosurfactants formed from a rhamnose-based hydrophilic head and one or more beta-hydroxy fatty-acid chains. They have attracted sustained scientific and industrial interest because their molecular structures can provide useful surface and interfacial activity in water-based and multiphase systems.

The term “rhamnolipid,” however, does not describe one uniform commercial material. It may refer to a defined molecule, a family of related congeners, a partially purified fermentation product or a formulated commercial grade. Two products with the same general name can therefore differ in composition, active content, physical form, impurities and performance.

This guide explains how rhamnolipid structure, production and purification influence product properties; how to interpret technical specifications; where commercial adoption is already visible; and what buyers and formulators should verify before evaluating a grade. The commercial side of that conversation is on our rhamnolipid biosurfactant page.

Rhamnolipids at a Glance

Question	Practical answer
What are rhamnolipids?	A family of glycolipid biosurfactants containing rhamnose and beta-hydroxy fatty-acid units.
Are they one molecule?	No. Natural and commercial products commonly contain mixtures of related congeners.
How are they produced?	Primarily by microbial fermentation followed by recovery, concentration and, where required, purification.
What do they do?	Depending on composition and formulation, they may support wetting, emulsification, detergency, foaming, dispersion and interfacial-tension reduction.
What are the main commercial directions?	Cleaning and selected personal-care applications currently provide the clearest public evidence of industrial-scale commercialisation.
What determines grade suitability?	Congener profile, active-content basis, product form, residual components, sensory properties, analytical controls, regulatory documentation and application testing.
Are all grades interchangeable?	No. Even products reporting the same purity can differ substantially.

1. Molecular structure and congener diversity
2. CAS numbers and chemical identification
3. How rhamnolipids are produced
4. Recovery and purification
5. Surface and interfacial properties
6. How to read a rhamnolipid specification
7. Analytical and performance testing
8. Application areas and commercial maturity
9. Formulation considerations
10. Sustainability: what should be verified?
11. Commercialisation challenges
12. How to evaluate a rhamnolipid supplier
13. Frequently asked questions
Conclusion
References

1. Molecular Structure and Congener Diversity

Rhamnolipids are amphiphilic molecules. Their rhamnose-containing region interacts favourably with water, while their fatty-acid region interacts with oils, hydrophobic soils and other non-aqueous phases. This combination enables adsorption at interfaces and the formation of aggregates in solution.

Mono-Rhamnolipids and Di-Rhamnolipids

The two broad structural groups are:

Mono-rhamnolipids, containing one rhamnose unit;
Di-rhamnolipids, containing two linked rhamnose units.

A commonly discussed mono-rhamnolipid is Rha-C10-C10, while a commonly discussed di-rhamnolipid is Rha-Rha-C10-C10. The notation describes the rhamnose head group and the approximate carbon-chain lengths of the beta-hydroxy fatty-acid units.

These are examples, not a complete definition of a commercial grade. Variations in chain length, saturation and the number or arrangement of fatty-acid units generate many possible congeners. Research using chromatographic and mass-spectrometric methods has demonstrated that fermentation products can contain complex congener distributions rather than only one mono- and one di-rhamnolipid.

Why Congener Distribution Matters

Changing the number of rhamnose units or the fatty-acid structure changes the balance between hydrophilic and hydrophobic behaviour. This can influence:

adsorption at air–water, oil–water and solid–water interfaces;
aggregate and micelle formation;
emulsification and solubilisation behaviour;
interactions with polymers, proteins and other surfactants;
sensitivity to pH, ions and formulation conditions;
foam, wetting and cleansing performance.

For this reason, a mono-/di-rhamnolipid ratio can be useful, but it is not a complete performance specification. The fatty-acid distribution, active-content basis and non-rhamnolipid components may also be important.

2. CAS Numbers and Chemical Identification

CAS identification is frequently oversimplified in online product listings. A CAS number linked to one defined congener should not automatically be assigned to every fermentation mixture.

For example, PubChem identifies a defined mono-rhamnolipid, Rha-C10-C10, under CAS 37134-61-5 and gives it the molecular formula C26H48O9. A defined di-rhamnolipid has a different structure, formula and identifier. Commercial mixtures may be described under other regulatory identities depending on their composition and registration history.

Identification level	What it may describe	Appropriate verification
Defined congener	One specified molecular structure	CAS, molecular formula, molecular mass and analytical standard
Congener-enriched grade	A mixture dominated by mono- or di-rhamnolipids	Chromatographic profile and stated calculation basis
Commercial rhamnolipid mixture	Multiple congeners plus water, salts or residual components	Supplier SDS, TDS, composition statement and grade-specific regulatory identity
Formulated product	Rhamnolipids combined with carriers or other ingredients	Full formulation identity and end-use documentation

The correct question is not “What is the CAS number for all rhamnolipids?” but “What substance or mixture is this specific commercial grade, and how is it identified in its supply and regulatory documents?”

3. How Rhamnolipids Are Produced

Microbial Fermentation

Rhamnolipids are most closely associated with Pseudomonas aeruginosa, although other natural or engineered microbial hosts have also been studied. Production involves converting a carbon source into rhamnolipid precursors and then assembling the hydrophilic and hydrophobic portions of the molecule.

In a simplified biosynthetic description:

fatty-acid metabolism supplies beta-hydroxy fatty-acid precursors;
the RhlA pathway contributes hydroxyalkanoyloxy alkanoic acid precursors;
RhlB catalyses formation of mono-rhamnolipids;
RhlC can add a second rhamnose unit to form di-rhamnolipids.

The resulting product profile depends on the organism, genes, fermentation medium, carbon source, nutrient balance and operating conditions.

Feedstocks and Process Conditions

Research has evaluated sugars, plant oils, glycerol, fatty materials and various side streams as carbon sources. A low-cost feedstock does not automatically produce a low-cost or consistent commercial product. Feedstock variability can affect fermentation control, impurity profiles, downstream processing and congener distribution.

Important process variables include:

carbon and nitrogen sources;
carbon-to-nitrogen ratio;
temperature and pH;
oxygen transfer and agitation;
foam control;
fermentation time;
strain stability;
titre, yield and volumetric productivity.

Rhamnolipids are themselves strong surface-active and foam-forming materials. Foam management can therefore become a central scale-up issue rather than a secondary operating detail.

Production Organism and Biosafety

The use of P. aeruginosa, an opportunistic pathogen, creates additional biosafety, containment and purification questions. Research groups and companies have explored attenuated strains and non-pathogenic or heterologous hosts to improve the production platform.

For a commercial grade, buyers should not infer safety from the word “biosurfactant.” They should ask:

which organism or production platform is used;
whether viable production organisms are absent from the finished material;
how microbial contamination is controlled;
what residual-cell, endotoxin or related impurity limits apply where relevant;
what toxicological and regulatory data support the intended end use.

The required evidence differs substantially between an industrial cleaner, an agricultural formulation and a personal-care ingredient.

4. Recovery and Purification

Fermentation produces a broth containing water, cells, nutrients, salts, metabolites, residual feedstock and a mixture of rhamnolipid congeners. Converting this broth into a consistent commercial product can require several downstream steps.

Depending on the target grade, processing may include:

biomass or cell separation;
pH adjustment and precipitation;
solvent or solvent-reduced extraction;
adsorption or membrane processing;
concentration;
decolourisation and deodorisation;
drying or granulation;
fractionation or higher-resolution purification.

Downstream processing affects both cost and product quality. A technical cleaning grade may tolerate colour or residual components that would be unacceptable in a personal-care or analytical grade. Conversely, extensive purification can increase price without adding value to an application that does not require it.

This is why “highest purity” should not automatically be treated as “best grade.” The appropriate target is sufficient and reproducible quality for the intended formulation, safety and regulatory requirements.

5. Surface and Interfacial Properties

Surface-Tension Reduction

Rhamnolipids adsorb at interfaces and can reduce the surface tension of water. Published values vary because researchers use different congeners, mixtures, concentrations, temperatures, pH values, electrolytes and measurement methods.

A headline value such as “reduces surface tension to 28 mN/m” is therefore incomplete unless the method and conditions are stated. It should not be used as a universal property of every rhamnolipid product.

Critical Micelle Concentration

The critical micelle concentration, or CMC, is the concentration range above which surfactant aggregates become significant under the stated test conditions. CMC values are often used to compare surface activity, but they are not fixed constants for the entire rhamnolipid family.

CMC can shift with:

congener composition;
purity and residual components;
pH and ionisation state;
ionic strength and counterions;
temperature;
measurement technique.

Low CMC alone does not prove superior cleaning or formulation performance. Cleaning, wetting, emulsification and foam behaviour must be assessed in the actual formulation and use conditions.

pH and Ionisation

Rhamnolipids contain a carboxylic-acid group. Their ionisation state changes with pH, influencing charge, solubility, aggregation and interactions with other formulation components. Acidification may reduce solubility or promote precipitation in some systems, while alkaline conditions may increase ionisation.

Any claim of stability across a wide pH range should therefore be supported by grade-specific data and should distinguish chemical stability, physical clarity, solubility and functional performance.

Wetting, Emulsification and Foam

Rhamnolipids may improve the spreading of aqueous solutions over hydrophobic surfaces, support oil–water emulsification and contribute foam. These functions are related but not interchangeable:

strong surface-tension reduction does not automatically guarantee fast wetting on every substrate;
a stable model emulsion does not prove long-term stability in a formulated product;
high foam volume is not always desirable in industrial or membrane cleaning;
detergency depends on soil type, substrate, mechanical action, temperature and the complete surfactant system.

Performance claims should identify the test method and the benchmark used.

6. How to Read a Rhamnolipid Specification

Active Content Is Not Always Purity

The terms “active matter,” “rhamnolipid content,” “glycolipid content,” “solids” and “purity” may be calculated by different methods. They should not be assumed to mean the same thing.

For example, a powder with high total solids may contain salts or other non-volatile components. A liquid grade may report active rhamnolipid on an as-supplied basis or on a dry basis. A colorimetric assay may also produce a different result from chromatographic quantification.

Before comparing prices, confirm:

what is being measured;
which analytical method is used;
whether the result is as supplied or calculated on a dry basis;
whether mono- and di-rhamnolipids are measured separately;
what makes up the balance of the product.

Recommended Specification Categories

Category	Parameters to consider
Identification	Product name, grade, regulatory identity, production route
Composition	Total rhamnolipid or glycolipid content, mono-/di-rhamnolipid profile, carrier or balance
Physical properties	Form, colour, odour, pH, density or bulk density, solubility or dispersibility
Residual components	Water, ash, salts, residual feedstock, solvents or process-related impurities where relevant
Performance	Surface tension, CMC, wetting, emulsification or foam tests with stated methods
Microbiological quality	Total counts, specified organisms and other application-relevant controls
Batch consistency	Specification limits, representative COAs and change-control expectations
Documentation	TDS, SDS, COA, composition statement, origin and application-specific regulatory data

7. Analytical and Performance Testing

Composition Analysis

Simple screening methods can indicate the presence or approximate amount of glycolipid material, but detailed congener analysis generally requires chromatography.

Methods encountered in research and industry include:

thin-layer chromatography for qualitative screening;
colorimetric methods for approximate rhamnose-related quantification;
HPLC with evaporative light-scattering or charged-aerosol detection;
LC-MS or LC-MS/MS for congener identification and more detailed quantification;
NMR and other spectroscopic methods for structural confirmation.

LC-MS/MS is particularly useful when congeners or positional isomers have similar chromatographic behaviour or molecular masses. A supplier stating only “tested by HPLC” should still explain the method, standard and calculation used.

Functional Testing

Useful tests depend on the intended application and may include:

equilibrium or dynamic surface tension;
interfacial tension against a defined oil;
CMC under stated conditions;
contact angle or substrate wetting time;
foam generation and decay;
emulsion formation and stability;
detergency against a defined soil and substrate;
hard-water tolerance;
pH, electrolyte and temperature stability;
compatibility with surfactants, polymers, enzymes, actives and preservatives.

The most informative qualification programme combines composition data with application testing. Neither one should substitute for the other.

8. Application Areas and Commercial Maturity

Rhamnolipids have been studied across a very broad range of industries. Published research potential should be distinguished from established, grade-specific commercial use.

Application area	Current interpretation	Main qualification questions
Home and industrial cleaning	Clear public evidence of commercial products and industrial-scale manufacture	Detergency, foam, wetting, hard-water behaviour, cost and ecolabel criteria
Personal care	Commercial activity exists for defined, documented grades	INCI identity, colour, odour, microbiology, impurities, safety and formulation compatibility
Agrochemical formulations	Technically promising and product-specific; regulatory treatment varies	Adjuvant versus active claim, crop and use pattern, formulation type and jurisdiction
Coatings and pigment dispersion	Emerging technical and commercial development	Substrate wetting, pigment dispersion, foam, coating defects and compatibility
Metal and membrane cleaning	Relevant niche evaluation area	Soil type, substrate compatibility, foam, rinseability and operating conditions
Environmental remediation	Extensive research and selected project-specific use	Contaminant, soil and water matrix, recovery, ecotoxicity, discharge and economics
Oil and gas	Significant research and specialised use potential	Salinity, temperature, adsorption, reservoir conditions, dosage and economics
Food and pharmaceutical uses	Research interest does not establish broad commercial approval	Purity, toxicology, regulatory approval, GMP and use-specific evidence

Cleaning

Cleaning currently provides some of the clearest commercial evidence. Evonik's REWOFERM RL 100 and RL 210 product information describes industrially produced rhamnolipid grades for applications including laundry, hard-surface, vehicle, metal and industrial cleaning. The company identifies cleaning, wetting, emulsification and foam performance as grade-specific benefits.

This does not mean every rhamnolipid mixture will reproduce the same performance. The published results belong to defined commercial products produced and formulated under controlled specifications.

Personal Care

Personal-care development values mild cleansing, foam quality, solubilisation, sensory properties and compatibility with skin and hair formulations. Yet this market also places tighter limits on odour, colour, microbes and process-related residues.

Commercial examples demonstrate another important point: ingredient identification can be product-specific. A defined commercial glycolipid grade may use an INCI identity that cannot be assumed for an unrelated supplier's fermentation product.

Agriculture

Potential roles include wetting, spreading, emulsification, dispersion and improved delivery of hydrophobic formulation components. Some rhamnolipid products or uses have also been investigated or registered for biological activity.

These two categories must remain separate. Marketing a material as a formulation aid is different from making fungicidal, pesticidal or plant-health claims. Registration for one composition and use in one country does not transfer automatically to another grade or market.

Coatings, Metal Cleaning and Membrane Cleaning

These applications may offer technically interesting niches because surface interaction matters and customers may value performance at relatively modest volumes. However, foam, substrate compatibility, residue, corrosion, rinseability and formulation stability can be decisive.

For membrane systems, the membrane material, foulant, cleaning pH, temperature and allowable foam must be defined. For metal cleaning, the alloy, soil, corrosion risk and subsequent process step should be included in the test design.

Environmental and Oilfield Applications

Rhamnolipids have been widely researched for hydrocarbon mobilisation, contaminant desorption, soil washing, bioremediation and enhanced oil recovery. These uses often face difficult economics because the required treatment volume can be large and matrices are highly variable.

Laboratory surface or interfacial activity is not enough to establish field viability. Adsorption losses, salinity, temperature, geology, contaminant composition, recovery strategy, discharge limits and delivered cost all need to be assessed.

9. Formulation Considerations

Compatibility with Other Surfactants

Rhamnolipids may be used alone or with anionic, non-ionic, amphoteric or other biosurfactants. Blending can change micellisation, foam, viscosity, solubilisation and deposition. Synergy should be demonstrated against a defined benchmark rather than assumed from ingredient class.

Polymers, Electrolytes and Actives

Because rhamnolipids can be ionised, they may interact strongly with charged polymers, proteins, metal ions and cationic ingredients. These interactions can be beneficial, neutral or destabilising depending on ratio and pH.

Formulators should monitor:

turbidity or precipitation;
viscosity drift;
loss of active performance;
phase separation;
foam changes;
deposition on surfaces;
preservative effectiveness.

Colour, Odour and Preservation

Fermentation-derived materials may carry characteristic colour or odour unless adequately purified. These features may be acceptable in industrial products but limiting in transparent or fragranced consumer formulations.

The finished formulation also requires its own preservation and microbiological assessment. A reported antimicrobial effect in a research assay should not be treated as proof of preservation efficacy or as permission to make an antimicrobial claim.

10. Sustainability: What Should Be Verified?

Rhamnolipids can be produced from renewable carbon through fermentation and may offer biodegradability advantages in defined products. However, the labels “bio-based,” “biosurfactant” and “biodegradable” answer different questions.

A meaningful sustainability assessment may consider:

feedstock source and land-use implications;
fermentation yield and energy demand;
water use;
foam-control strategy;
solvents and chemicals used in recovery;
purification intensity;
product concentration and transport;
aerobic and anaerobic biodegradation results;
aquatic-toxicity data;
application dosage and performance;
life-cycle boundaries and comparison basis.

One supplier's biodegradability or life-cycle result should not be attributed to the entire rhamnolipid class. Claims should follow the tested grade, method and regulatory framework.

11. Commercialisation Challenges

The opening of Evonik's industrial-scale rhamnolipid facility in Slovakia in 2024 was an important commercial milestone. It demonstrated that rhamnolipids had progressed beyond laboratory and pilot production for selected markets.

It did not remove the remaining industry-wide challenges:

fermentation economics and productivity;
foam management at scale;
downstream-processing cost;
congener and batch consistency;
colour, odour and residual impurities;
alignment of analytical methods;
application-specific toxicology and regulatory support;
price competition with mature conventional surfactants;
the gap between promising laboratory studies and validated customer formulations.

Near-term adoption is therefore most plausible where performance, sustainability positioning or formulation simplification can justify the cost and qualification effort.

12. How to Evaluate a Rhamnolipid Supplier

Manufacturing and Traceability

Is the company the actual producer, a formulator or a distributor?
Where is fermentation and downstream processing performed?
What organism and feedstock platform are used?
Is the commercial grade produced routinely or only on request?
How are batch traceability and change control managed?

Composition and Methods

What does the stated purity or active content mean?
Which method and reference standard are used?
Is mono-/di-rhamnolipid distribution reported?
Are water, salts, ash and residual components quantified?
Can the supplier provide representative chromatographic information when needed?

Quality and Documentation

Are the TDS, SDS and COA consistent with one another?
Are specification limits distinguished from typical values?
Which microbiological, residual-solvent or endotoxin controls apply?
Are biodegradability, ecotoxicology or safety claims supported by reports for the same grade?
Does the regulatory identity match the actual supplied composition?

Application and Commercial Support

Has the grade been tested in the intended application?
Can the supplier explain its test conditions and benchmarks?
Is an evaluation sample representative of normal production?
What are the confirmed MOQ, packaging, lead time and scale-up path?
Will the supplier support troubleshooting if the first formulation is unsuccessful?

These are the questions we work through before a grade is offered; what that review covers on our side is described on the rhamnolipid biosurfactant supply page.

13. Frequently Asked Questions

Are rhamnolipids natural surfactants?

They are microbial biosurfactants produced by fermentation. “Natural” may have a specific regulatory or marketing meaning in the destination market, so the allowed description should be confirmed for the particular product and process.

Are mono-rhamnolipids better than di-rhamnolipids?

Neither group is universally better. Their different structures can change interfacial and aggregation behaviour, but the preferred profile depends on the formulation, function and other product components.

What is the CAS number of rhamnolipid?

There is no single identifier that should automatically be applied to every rhamnolipid congener and commercial mixture. Use the grade-specific SDS and composition data, and distinguish a defined molecule from a mixture.

What is a typical rhamnolipid purity?

Commercial materials may range from relatively unpurified technical products to high-purity congener-enriched materials. A percentage is useful only when the measured substance, method and calculation basis are specified.

What is the CMC of rhamnolipids?

Reported CMC values vary with congener composition, purity, pH, ionic strength, temperature and method. Use a grade-specific value measured under stated conditions rather than one universal number.

Are rhamnolipids biodegradable?

Biodegradability has been demonstrated for defined commercial products and research samples, but the result depends on the grade, formulation and test method. Request the report supporting the product and claim being considered.

Can rhamnolipids replace SLS or SLES?

They may replace part or all of a conventional surfactant system in some formulations, but not necessarily at a one-to-one dosage. Foam, cleansing, rheology, stability, sensory properties and cost require formulation testing.

Are rhamnolipids suitable for cosmetics?

Some defined commercial grades are intended for personal care. This does not make all fermentation grades cosmetically suitable. INCI identity, impurities, microbiology, toxicology and regulatory documentation must be reviewed.

Can rhamnolipids be used in agrochemicals?

They may be evaluated for wetting, spreading, emulsification and other formulation roles. Any pesticidal, fungicidal or plant-health claim requires separate regulatory assessment for the specific product, use and market.

What should be tested first?

Begin with identity, composition, active-content basis, physical properties and representative COA data. Then test the grade in the actual formulation against an agreed benchmark under realistic water, pH, temperature and use conditions.

Conclusion

Rhamnolipids are no longer only a laboratory concept: industrial-scale production and defined commercial products now exist. At the same time, the category remains technically heterogeneous. Structure, congener profile, production organism, downstream processing and analytical basis can all change product quality and formulation behaviour.

For buyers and formulators, the most reliable approach is to start with the intended application, define the required function and regulatory market, compare methods rather than headline percentages, and qualify the actual grade through documentation and testing.

Palica Chem specifies the grade against the application, the documentation and the destination market it has to satisfy. Tell us what you are formulating on the rhamnolipid biosurfactant page, and we will come back with the grade and the documentation that goes with it.

References

Guzmán E, Ortega F, Rubio RG. Exploring the world of rhamnolipids: A critical review of their production, interfacial properties, and potential application. Current Opinion in Colloid and Interface Science. 2024;69:101780.
Kabeil SSA, Darwish AMG, Abdelgalil SA, et al. Rhamnolipids bio-production and miscellaneous applications towards green technologies: a literature review. PeerJ. 2025;13:e18981.
Chong H, Li Q. Microbial production of rhamnolipids: opportunities, challenges and strategies. Microbial Cell Factories. 2017;16:137.
Rudden M, Tsauosi K, Marchant R, Banat IM, Smyth TJ. Development and validation of an ultra-performance liquid chromatography tandem mass spectrometry method for the quantitative determination of rhamnolipid congeners. Applied Microbiology and Biotechnology. 2015;99(21):9177-9187.
PubChem. Mono-rhamnolipid, CID 162246 — CAS 37134-61-5, C26H48O9.
Evonik. REWOFERM RL 100 product information.
Evonik. REWOFERM RL 210 product information.
Evonik. RHEANCE D50 product information.
Evonik. Evonik drives sustainable biosurfactant revolution with inauguration of new facility in Slovakia. Press release, 29 May 2024.
US EPA. New Biopesticide Active Ingredients — 2004.