Biosurfactants

Surfactants (Surface active agents) are compounds with surface-active nature tendency to adsorb at interfaces. They are a very diverse group of lipids with a common amphiphilic nature; they contain both hydrophilic and hydrophobic domains within the same molecule. As a consequence, these compounds have lower interfacial tension allowing the solubilisation of hydrophobic substances in water. Biosurfactants are produced by microorganisms (biological origin), making them interesting since they can be obtained from renewable sources, in order to reduce the impact on the environment and the dependency on fossil resources. They play an important role in several industrial fields, such as household and industrial cleaning, cosmetic, nutritional and pharmaceutical industry. Additionally, surfactants can organise themselves in complex self-assembled supramolecular structures, such as micelles, liposomes or microemulsions. Thus, they can also be exploited as vehicle or carrier for active ingredients in the cosmetic, nutritional and pharmaceutical industry. Surfactants usually come from synthetic sources, represented mainly from the petrochemical or oleochemical sectors, like fatty alcohols. However, in recent decades, the large demand for surfactants has led to an increasing interest in obtaining them from renewable sources, in order to reduce the impact on the environment and the dependency on fossil resources. Moreover, biosurfactants typically exhibit a higher activity at lower concentrations compared to many synthetic surfactants, showing very low critical micelle concentration (CMC), low toxicity, high biodegradability and tolerance to extreme conditions such as high temperature values, extreme pHs, and high salinity.

Biosurfactants are also endowed with important biological activities making them more attractive from a commercial point of view. Consequently, there is now significant economic interest in biosurfactants, specifically for:

• their use in agriculture as a biocontrol agent thanks to their insecticide activity
• their application in bioremediation assisting hydrocarbon pollutant biodegradation and metal sequestering
• the chemical, food processing, food additives, cosmetic, and pharmaceutical industries for their emulsifying, foaming, dispersant, and antiadhesive activities
• medicine for their antimicrobial, antitumor, antiviral, and anti-inflammatory activities

Despite their significant advantages, the market of biosurfactants is still only 10% of the global surfactant market (EUR 3,66 billion compared to EUR 26 billion). This is mainly because of their higher cost compared to chemically derived surfactants and the limitations in the chemical diversity of molecules and producing microorganisms. This only emphasises that there is a need for better producing strains and tailor-made biomolecules to satisfy the requirements of the industry. Furthermore, to guide the selection of tailor-made biocompounds, it is necessary to expand the studies that are focused on the structure-property link of biosurfactants.