Biosurfactant

Vinay Kumar Singh. 
Head-Formulation
Kumar Organic Products Research Centre Pvt. Ltd.,
Bengaluru
Email : formulation_krc@kopresearchcentre.net

Biosurfactants, also known as biological surfactants/microbial surfactants, are secondary metabolites that are synthesized by a wide variety of microorganisms (bacteria, fungi and yeast) during their growth on the interface of hydrophilic and hydrophobic substrates. Biosurfactants are synthesized extracellularly and many microbes are known to produce biosurfactants in large relative quantities. Some are of commercial interest.Biosurfactants have carved a niche for themselves in the market due to their unique environment-friendly properties. They have come a long way since first biosurfactant “surfactin” was purified and characterized by Arima et al. (1968).

Recently from the global viewpoint chemical industry e.g. pharma, food, home care, personal are, petroleum etc. have recognized the potential of living cells in pretreatment of raw materials, processing operations, product development, waste management, energy recycling and conservation. In this scenario, surfactants are increasingly acknowledged for their wide range of applications. The huge market demand currently met by synthetic, petroleum based surfactants and also the stringent environmental guidelines, awareness to protect ecosystems have resulted in cumulative interest in microbial surfactants.

Global Biosurfactants Market size was over USD 1.75 billion in 2020 and is projected to raise at over 5.5% CAGR between 2021 and 2027 owing to rising consumer cognizance regarding the hazardous effects of manmade surfactants on environment and human well-being. Biosurfactantscan be extensively useful to many industrial fields such as petroleum, bioremediation, agriculture, cosmetics, food processing and pharmaceuticals because of their proven surface properties and biological activities.
Biosurfactants have several distinct properties compared to other synthetic surfactants, including mild production conditions, multifunctionality, higher biodegradability, and lower toxicity of living cells synthesis of active compounds. Due to their surface tension reducing, emulsion stabilizing, and biodegrading properties of these in place of chemical surfactants, they are generating huge demand in terms of research and usage. 

Biosurfactants are widely used in the food industry as food-formulation ingredients and antiadhesive agents as emulsifiers, de-emulsifiers, spreading agents, foaming agents, and detergents that find application in various fields such as agriculture, industrial sectors, and environmental recreation.Biosurfactants enhances the surface area of hydrophobic water-insoluble substrates that organism utilizes it for its growth and work efficiently in process of biodegradation, bioremediation and biocontrol.
Biosurfactants are amphiphilic compound that have hydrophilic and hydrophobic domains. The hydrophilic domains are usually consisting of carbohydrates, amino acids and phosphate groups. Hydrophobic domains are usually made up of long chain fatty acids. Classification of biosurfactants.
The biosurfactants are classified on the basis of its molecular weight and on the basis of its chemical composition. 

Classification based on molecular weight
1.    Low molecular- weight biosurfactants: These compounds lower the surface and interfacial tension at the air/water interfaces. The low molecular- weight biosurfactants are generally. glycolipids or lipopeptides. The glycolipids are till date best studied as rhamnolipids, trehalolipids and sophorolipids which are disaccharides that are acylated with long- chain fatty acids or hydroxyl fatty acids. 
2.    High- molecular weight biosurfactants: These are most commonly referred to as bioemulsan. They are more effective in stabilizing oil in water emulsions. They are highly efficient emulsifiers that work at low concentrations. It also bears extensive substrate specificity. Ron and Rosenberg (2001) reported that a large number of bacterial species from different genera produce exocellular polymeric surfactant composed of polysaccharides, proteins, lipopolysaccharides, lipo-proteins or complex mixtures of these biopolymers. When classification is based on their polar groupings most of the biosurfactants are either anionic or neutral and the hydrophobic moiety is based on long chain fatty acids or fatty acids derivatives whereas the hydrophilic portion can be carbohydrates, amino acid, phosphate or cyclic peptide stated that in general, the structure of a biosurfactants includes a hydrophilic moiety consisting of amino acids or peptides anions or cations, mono-, dior polysaccharides and a hydrophobic moiety consisting of unsaturated, saturated or fatty acids derivatives.

Classification based on Chemical Structure 
Glycolipids: Most known biosurfactants are glycolipids, they are carbohydrates whose constituent mono-, di-, tri and tetrasaccharides include glucose, mannose, galactose, rhamnose, galactose sulphate and glucoronic acid. These carbohydrates combine with long–chain aliphatic acids or hydroxyaliphatic acids. This linkage is by means of either ether or an ester group. In this taxa, the best known are the rhamnolipids, trehalolipids and sophorolipids. Other glycolipids produced by microorganisms are such as cellobiolipids.

Lipopeptides and Lipoproteins: A large number of cyclic lipopeptides including decapeptide antibiotics (gramicidin) and Lipopeptide antibiotics (polymxin) produced by bacteria, Bacillus brevis and Bacillus polymyxa that had remarkable surface active properties. It is consist of a lipid attached to a polypeptide chain). Fatty Acids, phospholipids and neutral lipids: several bacteria and yeast produces large quantities of fatty acids and phospholipids type of surfactant during growth on n-alkanes substrate. Fatty acids produced from alkanes are as a result of microbial oxidations that have been considered as surfactant. Apart from these straight chain acids, micro-organisms produce complex fatty acids containing OH groups and alkyl branches, example of such complex acids include corynomuolic acids.

Phospholipids: Phospholipids are major components of microbial membranes, when certain hydrocarbon degrading bacteria or yeast are grown on alkane substrates the level of the phospholipids increases greatly. When bacteria Acinetobacter sp HOI-N grown on Hexadecane substrate it produces the phospholipids that is mainly phosphatidylethanolamine.
Polymeric microbial surfactants: most of these biosurfactants are polymeric heterosaccharide containing proteins. The best studied polymeric biosurfactants are emulsan, liposan, mannoprotein and polysaccharide protein complexes.
Particulate Biosurfactant: there are some bacteria that produce extracellular membrane vesicles partition hydrocarbons that form micro emulsion. The microemulsions formed by them play an essential role in uptake of alkane by microbial cells.eg in case of Acinetobacter sp.

Properties of biosurfactant
a. It reduces the surface tension of water. 
b. They have excellent capacity of forming critical micelle concentration (CMC). 
c. The lethality of biosurfactants is very low. 
d. They have good compatibility and digestibility

Advantage of biosurfactants
Biosurfactants have many advantages when compared to chemically synthesized counterparts such as 
1. They are easily degraded by microbes. 
2. It has low toxicity. 
3. It has good compatibility and digestibility with other living organisms. 
4. They can be produced from cheap raw materials that are easily available in large quantities. 
5. It exhibits emulsification capacity. 6. They are ecologically accepted due to their property of maintaining sustainability.

The use of biosurfactants is presented as a best alternate option because of its versatility, biodegradability and eco-friendly nature that maintains sustainability of the environment in a much desired way.