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Essay: Bio surfactant production by marine bacterium Pseudomonas auriginosa strain

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  • Published: 15 October 2019*
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Bio surfactants are the surface active compounds produced by micro organisms in a wide range of surfaces. Basically bio surfactants are the compounds, lowers or affect the interfacial tensions between liquid to liquid and solid with liquid. They are amphiphatic in nature having both hydrophobic tail and hydrophilic head.

Classification of bio surfactants:

Bio surfactants are classified according to:

1. Molecular weight.

2. Physiochemical properties.

On the base of molecular weight:


On the base of physiochemical properties:


Structure of common bio surfactants:


Figure 1.common structure of biosurfactant

It contain hydrophilic head which is polar and soluble in polar solvents while tail is hydrophobic and non polar in nature ,non water loving so it is imissible in polar solvents.

1.2. Characteristics of bio surfactants:

There are various characteristics of the bio surfactants that make them adaptable in recent time and valuable. They have high degree of biodegradability, less toxic as compared to chemical surfactants that are harmful along beneficial advantages, cheaper and economically favorable because they  are produced by the mostly indigenous flora of the soil ,they are specific in production and do not produce harmful effects for the other indigenous flora and also not harmful for environment and they are efficient and effective in their action.

1.3. Chemical Structures of bio surfactants:


(a) structure of Polymixin B2 having polar head and long non polar tail.(b) structure of peptide bio surfactant (c) structure of Putisolvin II (d) structure of Pseudofactin II.

1.4 Industrial use of bio surfactants:

These are the natural products formed from bacteria ,yeast and fungi. There commercial value make them important .

Industrial usage of bio surfactant Percentage usage

Detergents industry 54%

Textile ,leather and paper industry 13%

Chemical industry 10%

Pharmaceutical and cosmetic industry 10%

Food industry


Other applications 3%



Mostly bio surfactants are produced from the petroleum derivatives.

Sources of bio surfactants:

There are different sources of  bio surfactants including :

 Micro-organism (bacterias) glycoloipids

 Yeast   sophorose lipids

 Plants  saponines

 Humans     glycolipids of human bile

Compounds that are derived from the microbial sources generally have emulsion capacity and reduce the surface tension.

1.6 Surface activity:

It is measured by the surface tension, interfacial tensions, emulsifying stability and distability and hydrophilic/ hydrophobic balance (HBL).

• Surface tension   force of attraction between the two liquids.

• Surface interfaces  limit between the two or more molecules to hold each other.

Surface tension I measured through tensiometer. Surface tension is reduced when the concentration of miceele is increased around the substrate. Micelle is the amphiphatic molecules that form aggregates around the substrate to reduce the surface tension between the two surfaces. Higher the critical micelle concentration (CMC),higher will be the reduction of surface tension.

Efficiency is measured through the CMC value and effectiveness is measured through the surface tension and interfacial tension.


Figure 3. relation between surface tension and CMC.


Figure 4.  Relation between physiochemical properties

1.7 Emulsions:

Emulsions are the tiny droplet /microscopic formed on the liquid surface when dispesed over the other liquid surface. There are two types of emulsions formed:

• Water in oil (hydrophobic)

• Oil in water( hydrophilic)

Higher the emulsion formed higher will be the reduction of surface tension. Hydrophilicity or the hydro phobicity tells about the relative solubility of the emulsion.

1.8 Substrates for bio surfactants:

Bio surfactants are produced on different substrates that are mostly hydrophilic in nature .e.g., solid liquid hydrocarbons, oils or fats. Industrial waste is most commonly used for the production of bio surfactants because industrial waste s rich in carbohydrates and lipids and could be serve as a ideal source for the growth of micro-organism e.g., cooking oil waste, cassava flour waste water, oil distillery waste, glycerine and soap stocks etc.

1.9 Classification according to biochemical nature:

This classification is based on the biochemical properties or according to the microbial specie that produce the bio surfactants.

• Glycolipids —- the rhamno lipids by Pseudomonas aureginosa.

• Lipo plysaccherides —- emulsan produced by the Acinotobacter calcoaceticus

• Lipo peptides —-surfactin produced by Baciilus subtilis.

• Phospholipids—-bio surfactants produced by Corynebacterium lepus.

• Neutral lipids—– different hydrophobic proteins.

1.10 Environmental applications:

Bio surfactants are gaining worth and known as a “multifunctional material” as use in nearly every industry. Bio surfactants play role in resolving various environmental issues. for example ,taking part in

Bio remediation (transfer of contaminents into less toxics), microbial enhanced oil recovery technique(MEOR).For enhanced recovery of oil, in washing of soil by removing the metal ions, cleaning of oil reserviours by reducing surface tension, some bio surfactants have pesticide specific activity that degrade it and protect the plants from chemical pesticides(HCH pesticide ).

1.10.1 Bio surfactant role in MEOR:

Microbial enhanced oil recovery is the technique t recover oil from the reseviours/ rocks through primary(natural flow), secondary (CEOR- chemical enhanced oil recovery by the use of chemicals)and tertiary techniques (MEOR- microbial enhanced oil recovery by the micro-organisms).in this technique, natural processes of micro-organisms are used such as bio surfactants ,biopolymers, biomass, bio acids, enzymes and biogases. Basically MEOR is applied to recover oil that is entrapped between the layers of the rocks. microbes produce bio surfactants reduce the surface tension and enhance the solubility of oil and cause the maximum and efficient recovery. Through this technique almost 70% of the oil is recover and then refined for the commercial purposes.

1.10.2. Mechanism of action:


In laboratory, mostly Pseudomonas species are used for bio surfactant production and applied on oil recovery technique by capillary methods. Although it is in-situ procedure but it could be tested in laboratories.

1.11 Bio surfactants produced by prokaryotes:

Rhamno-lipids are the best bio surfactants produced by the prokaryotic cells .they produce low molecular weight bio surfactants e.g., glycerol, ethanol, fructose by using different substrates molasses waste, pollutants waste (phenantherine), waste oil from reserviours. They reduce surface tension up-to 2mN/m ,have good emulsifying activity and most commonly used for the degradability purposes for the degradation of metal ions like copper and zinc.

1.12 Bio surfactants produced by eukaryotes:

In eukaryotes, mostly bio surfactants are produced by the yeast .Sophorose lipids and Mannosylerythrotol lipids. They use rapeseed, rinseed, safflower, soyabean and animal fats as a substrate to produce high molecular weight bio surfactant and have ability to reduce the surface tension up-to the 28mN/m.

1.13 Production methods for bio surfactants:

There are basis three different ways to produce the bio surfactants.1) production associated with the cell growth by using lipophilic substrates. 2)by giving limited growth conditions e.g., nitrogen limit. 3) using resting cells by making them immobilized on the substrate cells in the precursors form. Usually fed batch is used for the laboratory fermentation of bio surfactants.

1.13.1 Purification of the product:

Refining is done by the use of alcohols like chloroform, methanol, acetic acid, ether and ethyl acetates to purify extracted products.

1.14 Factors affecting the production of bio surfactant:

Source of carbon:

Carbon plays a necessary role in the growth of the micro organism and also for the bio surfactant production. Higher the amount of carbon source higher will be the growth and higher will be the bio surfactant amount produced. Industrial waste rich of carbohydrates is commonly used instead of simple glucose or other simple sources of carbon.

Source of nitrogen:

Nitrogen also plays important role in the growth and bio surfactant production. During fermentation reactions, carbon and nitrogen ratio is very critical, higher the ratio lesser will be the growth of micro organisms and lesser will be the bio surfactant produced. Ammonium nitrates are commonly used source of nitrogen.

Conditions for growth of microorganisms:

Growth conditions for the micro organisms are temperature, pH, oxygen supply. Growth conditions are varies from specie to specie or from organisms. So, optimum conditions according to the source will give higher growth and maximum bio surfactant production.


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