Rhamnolipids are a class of biosurfactants produced by various bacterial species, particularly Pseudomonas aeruginosa. These molecules have gained significant attention due to their unique properties and potential applications in various industries. Structurally, rhamnolipids consist of one or two rhamnose sugar molecules linked to one or more lipid (fatty acid) chains. This amphiphilic nature, with both hydrophilic and hydrophobic components, gives rhamnolipids their surfactant properties, allowing them to reduce surface and interfacial tensions between different phases. One of the most notable features of rhamnolipids is their ability to enhance the solubilization and biodegradation of hydrophobic compounds, such as oils, hydrocarbons, and other organic pollutants. This property makes them valuable in environmental remediation processes, where they can facilitate the removal of contaminants from soil and water. Additionally, rhamnolipids have shown potential in enhancing oil recovery from reservoirs in the petroleum industry. Rhamnolipids also exhibit antimicrobial and antifungal activities, making them promising candidates for use in various applications, including agriculture, food preservation, and healthcare. Their ability to disrupt cell membranes and inhibit biofilm formation contributes to their efficacy against a wide range of microorganisms. Furthermore, rhamnolipids have found applications in the cosmetic and personal care industries, where they can act as emulsifiers, foaming agents, and solubilizers. Their biodegradability and low toxicity make them attractive alternatives to synthetic surfactants in these products. The production of rhamnolipids can be achieved through microbial fermentation processes using various carbon sources, including renewable resources like agricultural residues and waste materials. This sustainable production method aligns with the growing demand for eco-friendly and bio-based products in various sectors. Despite their promising potential, the large-scale production and commercialization of rhamnolipids have been hindered by challenges related to cost-effective production processes and purification methods. Ongoing research efforts are focused on optimizing production strains, fermentation conditions, and downstream processing to overcome these challenges and facilitate the wider adoption of rhamnolipids in diverse applications.

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Biosurfactants - Rhamnolipids
A potent candidate in plant disease management
Sathiya Aravindan V
Department of Plant Pathology
Faculty of Agriculture
Annamalai University

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“
The future of crop protection is here
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 Introduction to rhamnolipids
 Production of rhamnolipids
 Antifungal activity of rhamnolipids
 Mechanism of action of rhamnolipids
 Use of rhamnolipids as biofungicides
 Advantages and disadvantages of
rhamnolipids
 Future research directions
Table of contents

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Introduction and history rhamnolipids

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Introduction to Rhamnolipids
Rhamnolipids are
the biosurfactants
composed of sugar
Rhamnose +
lipopeptide
The lipid molecules
are linked to
rhamnose sugar
moiety
They are amphiphilic
in nature (Both
hydrophobic and
hydrophilic in
nature)
Secondary
metabolites
extracted from non
pathogenic strains of
bacteria
They are one of the
members of the
Glycolipids

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Prologue of rhamnolipids
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1946 • Rhamnolipids were first isolated from the bacterium Pseudomonas aeruginosa
1970
• Rhamnolipids were first studied for their potential use as biosurfactants
1986
• Rhamnolipids were first shown to have antifungal activity
1990
• Rhamnolipids were first used to control plant diseases in greenhouse trials.
2001
• Rhamnolipids were first used to control plant diseases in field trials.
2010
• Rhamnolipids were commercialized as a bio fungicide.
2020
• Rhamnolipids were being investigated for their potential use in other areas of plant
health, such as seed treatment and plant growth promotion.
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Production of rhamnolipids

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Production aspects of rhamnolipids
Synthesis of rhamnose sugar Synthesis of lipid

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Production of the sugar
dtDP-L-Rhamnose
(Deoxythymidine diphospho- L –rhamnose)
D-Glucose -1 -P
RmL A RmL B RmL C RmL D
D-Glucose -6 -P
(AlgC)

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Production of lipid moiety
Pictorial representation of Rhamnolipids
synthesis

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Mono-rhamno-mono-lipid
One of the most commonly
existing form of rhamnolipids
is Mono-rhamno-mono-lipid
It consists of single unit of
rhamnose (Sugar) and single
unit of lipid

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Mono-rhamno-di-lipid
This form of rhamnolipids is
Mono-rhamno-di-lipid
It consists of single unit
of rhamnose (Sugar) and
two units of lipid

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Di-rhamno-mono-lipid
This form of rhamnolipids is
Di-rhamno-mono-lipid
It consists of single unit of
rhamnose (Sugar) and two
units of lipid

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Di-rhamno-mono-lipid
This form of rhamnolipids is
Di-rhamno-mono-lipid
It consists of single unit of
rhamnose (Sugar) and two
units of lipid

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Other members of glycolipids
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There are several members of glycolipids including
 Trehalolipids
 Sophorolipids
 Mannosylerythritisol
 Trehalose dimycolate
 Lipopeptides
 Lipopeptides and Rhamnolipids were the most investigated
from the class of glycolipids

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Factors that makes the Rhamnolipids a potential
candidate in plant disease management
Why
rhamnolipids
over others?
Eco-
friendly
Easily
degradable
Also
activates the
innate
immune
response
Extremely low
spray
concentration
Compatibility
with other
bio-control
agents
Extremely
low toxic

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Antifungal activity of rhamnolipids
Mechanism of
rhamnolipids
Sporangial
lysis
Disrupt
plasma
membrane
permeability
Mycelial
degeneration
Zoospore lysis

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•Rhamnolipids can be applied to plants as a foliar spray or as
a drench.
•They are most effective when applied early in the infection
process.
•Rhamnolipids can be used in combination with other
biofungicides or conventional fungicides to improve their
effectiveness.
•They are not registered for use on all crops, so it is important
to check with the manufacturer before using them.
Use of rhamnolipids as biofungicides

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Advantages and Disadvantages of
Rhamnolipids

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Advantages of Rhamnolipids
Eco-friendly and sustainable: Rhamnolipids are produced from
renewable resources, such as sugar, and are biodegradable. This makes
them a more sustainable alternative to synthetic surfactants, which are
often derived from petroleum.
Low toxicity: Rhamnolipids are generally considered to be non-toxic, even
at high concentrations. This makes them safe for use in a variety of
applications, including food and cosmetics.
Excellent foaming properties: Rhamnolipids are excellent foaming agents,
which makes them useful for a variety of applications, such as enhanced oil
recovery and cleaning.

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Disadvantages of Rhamnolipids
High production cost: The production of rhamnolipids is currently relatively
expensive. This is due to the high cost of the raw materials and the complex
fermentation process required to produce them.
Foaming problems: Rhamnolipids can form excessive foam during
production and use. This can be a problem in some applications, such as
enhanced oil recovery.
Potential toxicity to some organisms: Rhamnolipids have been shown to be
toxic to some organisms, such as algae. This is a potential concern for
environmental applications.
Unstable: They are highly unstable when exposed to sunlight

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Hallmark innate resistant mechanism in plants due
to Rhamnolipids
The activity or the levels of
Callose deposition
Phytohormone increases
Defense gene activation
Ca ions influx
ROS (Reactive Oxygen Species)
Phosphorylation cascades
HR responses

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Other commercial uses of Rhamnolipids
 They are used in bioremediation agent in controlling the oil-spills
 Use in detergents and in the surfactants
 Indirectly induces the Phytohormones levels
 Used in cosmetics

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 These rhamnolipids are the bio surfactants which comes under the glycolipids
 They are produced by the bacteria and fungi as their secondary metabolites
 They can sprayed either with the carrier molecule or in their purified form
 The purified form of the mono and di-rhamnolipids are found to be highly effective
 Found synergistic effect with the compatible bio-control agents
 Application of rhamnolipids along with the Rhodotorula glutinis is also found be highly
effective (Synergistic effect)