Microbial surfactants: A journey from fundamentals to recent advances

Abstract

Microbial surfactants are amphiphilic surface-active substances aid to reduce surface and interfacial tensions by accumulating between two fluid phases. They can be generically classified as low or high molecular weight biosurfactants based on their molecular weight, whilst overall chemical makeup determines whether they are neutral or anionic molecules. They demonstrate a variety of fundamental characteristics, including the lowering of surface tension, emulsification, adsorption, micelle formation, etc. Microbial genera like Bacillus spp., Pseudomonas spp., Candida spp., and Pseudozyma spp. are studied extensively for their production. The type of biosurfactant produced is reliant on the substrate utilized and the pathway pursued by the generating microorganisms. Some advantages of biosurfactants over synthetic surfactants comprise biodegradability, low toxicity, bioavailability, specificity of action, structural diversity, and effectiveness in harsh environments. Biosurfactants are physiologically crucial molecules for producing microorganisms which help the cells to grasp substrates in adverse conditions and also have antimicrobial, anti-adhesive, and antioxidant properties. Biosurfactants are in high demand as a potential product in industries like petroleum, cosmetics, detergents, agriculture, medicine, and food due to their beneficial properties. Biosurfactants are the significant natural biodegradable substances employed to replace the chemical surfactants on a global scale in order to make a cleaner and more sustainable environment.

Rhamnolipid Self-Aggregation in Aqueous Media: A Long Journey toward the Definition of Structure–Property Relationships

“…However, both the use and the synthesis of surfactants are associated with unfavorable environmental issues that represent an increasing concern worldwide. Most surfactants are produced from petrochemical resources by means of polluting industrial processes [ 26 , 27 , 28 ]. Moreover, they can cause allergic reactions and skin irritation [ 29 , 30 , 31 ] and, when dispersed in the environment, may be toxic to different organisms [ 25 , 32 , 33 , 34 ].…”

“…For these reasons, the development of environmentally friendly surfactants with good biodegradability is in great demand [ 35 ]. In this respect, an attractive and promising alternative to commonly used synthetic surfactants is represented by so-called biosurfactants [ 1 , 2 , 4 , 19 , 26 , 36 , 37 , 38 ]; these are surfactants naturally derived from microorganisms, such as bacteria and yeasts [ 4 , 19 , 26 , 28 , 39 , 40 , 41 ]. However, this term is often used in a larger meaning to indicate not only surfactants extracted from natural sources or produced enzymatically or microbially, but also those surfactants that are chemically synthesized from biomass, such as sugars, plant oils, and amino acids [ 27 , 42 ]; for the latter class, a more appropriate term should be bioderived or bioinspired surfactants, and they should be discussed as a class of their own [ 4 ].…”

“…Biosurfactants are usually classified on the basis of their molecular weight, a distinction due to Rosenberg and Ron [ 43 ], rather than the features of the polar head, as happens for canonical synthetic surfactants; hence, biosurfactants are divided into low-molecular-weight (LMW) and high-molecular-weight (HMW) ones ( Figure 1 ) [ 2 , 28 , 38 , 43 , 44 , 45 ]. Glycolipids and lipopeptides belong to the former class, while polymeric compounds, such as proteins, polysaccharides, and combined forms of lipoproteins or lipopolysaccharides belong to the latter [ 2 , 41 , 45 , 46 ].…”

“…At the same time, an increasing number of applications of rhamnolipids have been discovered and investigated in the last few years, as discussed in numerous papers [ 2 , 19 , 28 , 39 , 44 , 45 , 49 , 50 , 53 , 100 , 104 , 105 , 120 , 121 , 122 , 123 , 124 , 125 , 126 , 127 , 128 , 129 , 130 , 131 , 132 , 133 , 134 , 135 , 136 , 137 , 138 , 139 , 140 , 141 ].…”

Production and characterization of bioemulsifier by Parapedobacter indicus

“…Biosurfactants and BE have gained increased importance in recent years due to their potential applications in various industries such as pharmaceutical, agriculture, food, medicine, textile, and oil industry ( Kumar et al, 2021 ; Raj et al, 2021 ; Dong et al, 2022 ; Pardhi et al, 2022 ; Thraeib et al, 2022 ). They play a key role in industries by exhibiting different properties such as surface and interfacial tension reduction, wetting agent, oil dispersion, cleansing agent, and emulsification ( da Silva Lira et al, 2022 ).…”