What are Biosurfactants?

By Stefano Tommasone Ph.D.Reviewed by Megan Craig, M.Sc.

Surfactants are amphiphilic molecules widely used in several industries. However, their synthetic origin poses concerns regarding toxicological effects and environmental impact. Hence, there is a major drive towards the development of surfactants from biological sources, namely biosurfactants, with more sustainable and eco-friendly methods.

Biosurfactants – surface active agents of microbial origins – can replace their synthetic analogs in sectors such as the pharmaceutical, agriculture, cosmetics, and oil industry. They are less toxic, biodegradable, and possess lower critical micelle concentration values.

With higher tolerance to pH and temperature, and emulsifying ability, biosurfactants also show antimicrobial properties, and given their ability to form micelles they can be used as drug delivery systems.

Understanding Biosurfactants

The amphiphilic nature of biosurfactants is due to the presence of hydrophilic heads – containing amino acids, mono-, di-, or polysaccharides – and hydrophobic tails made of chains of 10-18 carbon atoms or fatty acids.

The chemical composition varies significantly depending on multiple factors. Biosurfactants are divided into two categories based on their mass: low molecular weight compounds, such as glycolipids and lipopeptides, are normally used to reduce surface tension; high molecular weight compounds, like lipoproteins and polymeric biosurfactants are effective emulsifiers.

Glycolipids contain mono and disaccharides linked to long-chain aliphatic acids, and are the most common type of biosurfactants. This group includes trehalolipids, sophorolipids, and rhamnolipids.

Lipopeptides consist of cyclic peptides linked to the fatty acid chain, such as surfactin, where a lactone links a ring structure with seven amino acids to a fatty acid chain.

Polymeric biosurfactants are a complex mixture of biopolymers (e.g., proteins and polysaccharides) linked to fatty acids via o-ester bonds. Examples are emulsan, liposan, and mannoprotein.

How Do Biosurfactants Work?

Their molecular structure allows biosurfactants to lower surface tension (the capacity of a liquid to resist external forces), to be used in emulsification and solubilization processes, and to promote the adsorption of bioactive molecules through biological membranes.

When they reach a concentration above a threshold known as critical micelle concentration (CMC), they assemble together forming micelles. The hydrophilic heads align in polar solvents such as water, whilst the hydrophobic tails gather together in the micelle’s core. This property is used to reduce contaminants, like in the removal of oil from water or soil.

Manufacturing of Biosurfactants

The production of biosurfactants involves enzyme-substrate reactions and fermentation processes of microorganisms such as bacteria, filamentous fungi, or yeast. Depending on the substrates used (glucose, fructose, alkenes, citrates, etc.) biosurfactants with different properties can be produced.

For instance, rhamnolipids are mostly produced by Pseudomonas and Burkholderia species. The environmental and growth conditions affect the chain length, degree of branching, and degree of unsaturation in the fatty acid chains.

Sophorolipids can be produced by several non-pathogenic yeasts. The most used species are genus Candida. In particular, C. bombicola and C. apicola contain the enzymes necessary for the terminal oxidation of alkanes to generate fatty acids.

Applications Across Industries

A promising area of application of biosurfactants is environmental bioremediation. They facilitate the degradation of hydrocarbons in contaminated water and soil, and can be used in wastewater treatment, oil spill response, and removal of heavy metal contaminants.

Microorganisms are able to metabolize oil-related compounds in the biodegradation process. The pollutants are used as carbon and energy sources and ultimately transformed into CO₂, water and minerals.

Rhamnolipids were investigated for the bioremediation of soils containing 6800 ppm and 8500 ppm total petroleum hydrocarbon (TPH) and showed higher degradation efficiency (86.1% and 80.5% respectively) than synthetic surfactants (70.8% and 68.1%).

Other interesting applications of biosurfactants are found in the pharmaceutical industry, thanks to their antimicrobial, antiviral, anti-inflammatory, and immunomodulatory properties. Surfactin has shown antifungal activities as well as the ability to inhibit the fibrin clotting process. It also showed antitumor activity against Ehrlich’s ascites carcinoma cells.

The low toxicity and dermal compatibility make biosurfactants suitable replacements of petroleum derivates in the cosmetic industry. Sophorolipids are suitable for the treatment of acne, dandruff, and body odors. Rhamnolipids are used in the formulations of deodorants, nail care products, and anti-wrinkle agents, while anti-aging skincare products have been prepared with mannosylerythritol lipids.

Environmental and Commercial Benefits

Current societal concerns with regard to climate change and environmental protection are urging a shift in the use of materials derived from petrochemicals toward using substitutes from renewable and sustainable sources.

Properties like biodegradability are driving the interest in the development of biosurfactants. Additional benefits include low toxicity, production from renewable sources and tolerance under extreme pH and temperature conditions.

Also, as described earlier, biosurfactants are known to have properties like self-assembly, reduction of surface tension, emulsification, and adsorption, which make them suitable for various applications.

In 2022, the global biosurfactants market was valued at $1.2 billion, and it is expected to increase to $1.9 billion by 2027. Over half of the biosurfactants market is focused in Europe, where the main manufacturers are Evonik, Biotensidon, BASF, Solvay and Holiferm. Other key players are in the United States, with Jeneil Biotech, and Asia, with companies like Deguan Biosurfactant Supplier (China) and Allied Carbon Solutions Co. (Japan).

Locus Fermentation Solutions recently launched FloBoost, a biosurfactant used in saltwater disposal wells (SWDs) that can reduce costs in oilfield applications, whilst Holiferm announced a partnership with Sasol aiming to commercialize sophorolipids in the Middle East and develop novel biosurfactants.

Challenges and Future Prospects

With an increasing number of manufacturers interested in producing eco-friendly products from sustainable sources, biosurfactants have become an attractive alternative to synthetic surfactants.

One of the major limitations is the high production costs, mainly due to the fermentation and product purification steps. The prices of biosurfactants are in fact, significantly higher than those of synthetic surfactants.

There is, however, a lot research focused on the development of optimized conditions for biosurfactants production that could be more economically viable and productive. Potential ways to tackle these problems and reduce the costs may lie in the investigation of different microorganisms and plants as alternative sources, as well as the use of oil byproducts and food waste.

Further Reading

• All Agriculture Content
• How Biofortification Strengthens Food Security