A Review on Microbial Surfactants: Production, Classifications, Properties and Characterization

Abstract

Surfactants are a surface-active group of molecular compounds with hydrophobic and hydrophilic moieties in one single molecule that distributes themselves between two immiscible fluids, reduce surface/ interfacial tensions and cause the solubility of non-polar compounds in polar solvents. Besides surface and interfacial activities, they display properties such as solubilization, detergency, lubrication, emulsification, stabilization and foaming capacity. Microbiologically derived surfactants are called biosurfactants. They are produced as either metabolic products or as the surface chemistry of an actual cell. The employment of screening techniques such as surface tension measurements, drop collapse test, oil spreading assay, emulsification index (%EI24), cetyltrimethylammonium bromide (CTAB)/methylene blue agar plate test and strain characterization. Others are analytical techniques including liquid chromatography-mass spectroscopy, thin layer chromatography, high-performance liquid chromatography, Fourier transform infrared spectroscopy, nuclear magnetic resonance, fast atom bombardment-mass spectrometry and electrospray Fenibo et al.; JAMB, 18(3): 1-22, 2019; Article no.JAMB.51198 2 ionization-mass spectrometry. These have led to the identification of biosurfactant producing microorganisms, properties and characterization of biosurfactants. Therefore, this review tends to provide the current knowledge of the screening techniques and chromatography/spectroscopic tools employed to study biosurfactants. Results from a detailed study of these tools can unveil new surfactant producing microorganism, decipher chemical diversity and multifunctional properties of biosurfactants critical for applications in diverse industrial sectors. Review Article

Biosurfactants: Eco-Friendly and Innovative Biocides against Biocorrosion

“…These compounds are known to exhibit broad-spectrum antimicrobial activity, and different classes of biosurfactants are being used by the agricultural, oil, food, cosmetic, biotechnological, and pharmaceutical industries, as well as in a wide range of environmental remediation technologies [24,[28][29][30][31][32][33][34][35]. The review of Fenibo et al [36] offers an overview of diverse applications of biosurfactants, with emphases on petroleum biotechnology, environmental remediation, and the agriculture sector. Once synthesized by the microorganism, the biosurfactants are either secreted extracellularly or are partially attached to the membrane of the cell [37].…”

Surfactants of microbial origin and its application in foods

“…Their chemical structure in: glycolipids, lipoproteins or lipopeptides, phospholipids, fatty acids or natural lipids, polymeric surfactants and surfactant particles (Santos et al, 2016;Varjani and Upasani, 2017), and 2. Based on its molecular weight: (a) low molecular weight compounds such as: glycolipids, lipopeptides, short chain grade acids and phospholipids, and (b) high molecular weight compounds such as: polymeric surfactants, lipopolysaccharide surfactant particles or lipoproteins considered bioemulsifiers (Sourav et al, 2015;Varjani and Upasani, 2017;Kubicki et al,2019;Fenibo et al, 2019). Stressing that BS reduces surface and interfacial tension while bioemulsifiers are more effective in stabilizing oil-in-water emulsions (Varjani and Upasani, 2017).…”

“…The physiological function of the BS in the producing cell is not fully understood yet, but it is believed that these compounds are synthesized and released to facilitate the transportation, absorption and metabolism of hydrophobic compounds by solubilization and emulsification processes, as well as acting as biocidal agents in the survival and competition in ecological niches (Dhanarajan and Sen, 2014;Chavez et al, 2016;Santos et al, 2016;Fenibo et al, 2019).…”

“…On the other hand, the synthesis of BS can be affected in quality and quantity by factors such as the nature of the carbon source (lipophilic or hydrophilic), nitrogen source, pH, temperature, aeration, agitation, metal ion concentration, incubation time, culture strategy (batch, fed-batch, continuous), dilution rate and cell stress conditions like low concentration of the nitrogen source (Saharan et al, 2011;Sourav et al, 2015;Usman et al, 2016;Santos et al, 2016;Fenibo et al, 2019).…”

“…Some methods have been developed for the search and detection of BS-producing microorganisms in nature such as phenotypic tests that is, hemolytic activity, emulsification index, blue agar plate method, hydrocarbon agar plate, drop collapse, or oil spreading; also, there are molecular techniques through the polymerase chain reaction (PCR); while, on the other hand, physicochemical and instrumental methods have been developed focused on the recovery, purification and characterization of these compounds that involve the use of organic solvents, acid precipitation, alkaline precipitation, crystallization, filtration, ultrafiltration, lyophilization, centrifugation, layer chromatography fine, ion exchange chromatography, high pressure liquid, gas chromatography coupled to mass spectrometry, infrared, nuclear magnetic resonance, matrix assisted laser desorption / ionization with ion detector, and mass spectrometry (MALDI-TOF MS) (Satpute et al, 2010;Saharan et al, 2011;Sachdev and Cameotra, 2013;Sourav et al, 2015;Mnif and Ghrib, 2016;Santos et al, 2016;Varjani and Upasani, 2017;Fenibo et al, 2019).…”