Microbial Biosurfactants

Dear Colleagues,

Surfactants (surface-active compounds) are amphipathic compounds, i.e., they have both a hydrophilic and a hydrophobic group. They preferentially accumulate at the interface (hence the name surfactant), e.g., oil–water or air–water. The non-polar part is often a hydrocarbon chain, while the polar region can be ionic (cationic or anionic), non-ionic, or amphoteric. Microbial surfactants (biosurfactants) most often are divided according to the chemical structure of the hydrophilic part, which can be, e.g., sugar or peptide. Such a general chemical structure allows the biosynthesis of a wide variety of chemical compounds. In turn, this diverse chemical structure allows for the obtaining of biosurfactants with a wide range of properties. In fact, very often microorganisms produce not one chemical compounds but a mixture of biosurfactants. Hence, many studies focus on isolation, the identification of the chemical structures, and the investigation of the properties of biosurfactants.

Biosurfactants have been studied for many years, and interest in these substances is growing. This is due, among other things, to the enormous economic importance of surfactants and the desire to replace synthetic compounds with natural, environmentally friendly substances produced from biomass (green chemistry). The most significant limitation on the large-scale production of biosurfactants and their widespread use is the high cost of their manufacturing. This results most often from the low concentration of biosurfactants in the fermentation medium and the expenses associated with fermentation and downstream processing. Much research has focused on these issues, but so far, it has not led to widespread commercialization and significant price reduction.

The varied structure and different properties resulting from the chemical structure are another broad and exciting issue. The different properties are associated not only with the features typical of surfactants such as reducing surface tension, foam formation, micelle formation, or the formation of stable emulsions, but also their biological properties such as anti-microbial or anti-cancer activity. The mechanism of action, as well as the relationship between chemical structure and observed activity, are still often not fully understood. It is even more methodologically challenging to study the biological significance of biosurfactants for the microorganisms that produce them. It seems that a range of various chemical compounds with similar properties can perform the same biological function. The reverse can probably also be true. Compounds with similar structures and chemical properties may have different biological functions, depending on the type of microorganism. This area remains largely unexplored.

We hope that this Special Issue will give a platform for both academic and industrial researchers to exchange information. Thus, it could lead to a synergistic effect and expand our knowledge beyond boundaries those that exist today.

We cordially invite you to submit research articles, review articles, and short communications related to various interdisciplinary aspects related to biosurfactants.

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• Biosurfactant production
• Biosurfactant purification
• Functional properties
• Industrial applications
• Green chemistry
• Lipopeptides
• Glycolipids