Usefulness of bioemulsifiers and biosurfactants for environmental and medical applications
Bioemulsifiers are amphipathic polymers while as biosurfactants are surface active chemicals produced by large number of bacteria, fungi and yeasts. They have multiple applications in medicine, industry, pharmacy, agriculture and environment. Their unique structures and physicochemical properties determine their applicability in various fields. There is large variability in their production, surface active properties, rheological properties and chemical composition. Depending upon their chemical nature, they have been classified as high molecular weight (BE) and low molecular weight (BS) compounds. Bioemulsifiers are composed of polysaccharides, proteins, lipopolysaccharides, lipoproteins or complex mixtures of these biopolymers. Biosurfactants are generally glycolipids or lipopeptides in which rhamnolipids, trehalolipids and sophorolipid compounds predominate. Certain advantageous characteristics of both BE and BS makes them suitable for environmental applications, such as their biodegradability, compatibility to environment, very less or no toxicity to flora and fauna of different ecosystems. They are known to increase the bioavailability of carbon sources. They are applied in relatively low concentration and are functionally effective at extremes of pH and temperature or other extreme environmental conditions. They are found to be functionally substrate specific and generally do not imbalance the original form of ecosystem. Their commercial production is cost-effective in terms of substrate and production medium utilized or media components and substrates can be obtained from cheaper sources like agro-industrial wastes. It has also been possible to produce BS especially, at contaminated sites. For this, producing microbe can be isolated and exploited for exact application like microbes isolated from metal contaminated soils could be utilized for the remediation of that metal. Being amphipathic molecules, their hydrophilic and hydrophobic moieties tend to partition at interface between different fluid phases like water in oil or oil in water with different degrees of polarity. This criterion is the most important for environmental applications of these biomolecules. These advantages of bioemulsifiers and biosurfactants over their chemical counterparts make them promising for environmental applications. Some important applications are microbially enhanced oil recovery (MEOR), biodegradation, heavy metal recovery, rhizoremediation, phytoremediation and biological control. In addition to this, they contribute in ecologically important functions of microorganisms such as biofilm formation and establishment, chemotaxis and quorum sensing, pathogenesis related phenomena and help to establish the microbes in their microhabitat.
Use of BS as antimicrobial agents is well known. Biosurfactants produced by Bacillus are already in use as antibiotics for therapeutic purposes. Surfactin produced by Bacillus subtilis has been used for inhibition of fibrin clot formation, hemolysis and formation of ion channels in lipid membranes. It has shown antitumour activity against carcinoma cells, antiviral activity against human immunodeficiency virus (HIV-1) and antimycoplasma activity. Pumilacidin from Bacillus pumilus has antiviral activity against herpes simplex virus, Iturin from Bacillus subtilis was shown to possess antimicrobial activity and antifungal activity against profound mycosis. Lichenysin of Bacillus licheniformis has potent antibacterial activity and chelating properties. Surfactant of Lactobacillus is used as probiotic drugs for maintenance of healthy intestinal and urogenital tract. Rhamnolipid BS of Pseudomonas aeruginosa has antimicrobial activity against Mycobacterium tuberculosis. Viscosinamide from P.fluorescens have potent antimicrobial activity. In addition to this, surfactant and emulsifiers from Candida antartica, Torulopsis bombicola and Rhodococcus erythropolis have been utilized as important therapeutic agents. Biosurfactants have been found to inhibit the adhesion of pathogenic organisms to solid surfaces or to infection sites hence they are also used as antiadhesives in medical practice. Surfactin of Bacillus and surlactin of Lactobacillus have potential application as antiadhesives agents for the prevention of infection by streptococci and enteric bacteria respectively. Spiculisporic acid, sophorolipids and lipopeptide from Penicillium spiculisporum, Torulopsis bombicola and Bacillus sp. respectively have been used in cosmetic formulations and biosoap production. Bioemulsifiers also find tremendous applications in food industries. So what makes BS and BE so useful in medical field? First desired property is that some BS and BE have antibacterial, antifungal and antiviral activities which make them promising candidates for the treatment of diseases as therapeutic agents. They exhibit different chemical structures, such as glycolipids, lipopeptides, polysaccharide-protein complexes, phospholipids, fatty acids and neutral lipids which give advantage to modify them structurally and functionally for various physiological functions. It is possible to genetically manipulate or alter their structure to selectively enhance antimicrobial profile. They can be tailor-made to suit different applications by changing the growth substrate or growth conditions during their production. They are non-toxic with limited antigenic and side effects. Bioemulsifiers form emulsions and stabilize them. In addition to this, they are biodegradable, less viscous, high polysaccharide containing and non- toxic and can be produced on ecofriendly wastes of agricultural origin. These properties make them useful in food processing and formulation. They can also be manipulated to function at physicochemical extremities like temperature which is essential during cosmetic formulations. Their production by ecofriendly, economical and cost effective processes as compared to synthetic drugs makes them very suitable for environmental as well as medical applications.
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