Formation and stabilization of nanoemulsions using biosurfactants: Rhamnolipids

Abstract

Nanoemulsions are used in the food, cosmetics, personal care and pharmaceutical industries to provide desirable optical, textural, stability, and delivery characteristics. In many industrial applications, it is desirable to formulate nanoemulsions using natural ingredients so as to develop label-friendly products. Rhamnolipids are biosurfactants isolated from certain microorganisms using fermentation processes. They are glycolipids that have a polar head consisting of rhamnose units and a non-polar tail consisting of a hydrocarbon chain. In this study, the interfacial characteristics of this natural surfactant at medium chain triglyceride (MCT) oil-water interfaces were characterized, and its ability to form nanoemulsions was compared to that of another natural surfactant (quillaja saponins). The influence of rhamnolipid concentration, homogenization pressure, and oil type on the mean droplet diameter of emulsions produced by microfluidization was determined. Rhamnolipids were highly effective at forming small droplets (d32<0.15μm) at low surfactant-to-oil ratios (SOR<1:10) for MCT oil. Rhamnolipids could also be used to form small droplets using long chain triglyceride oils, such as corn and fish oil. Rhamnolipid-coated droplets were stable to aggregation over a range of pH values (5-9), salt concentrations (<100mM NaCl) and temperatures (20-90°C). However, droplet aggregation was observed at highly acidic (pH 2-4) and high ionic strength (200-500mM NaCl) conditions. These effects were attributed to a reduction in electrostatic repulsion at low pH and high salt levels. Rhamnolipid-coated droplets had a high negative charge at neutral pH that decreased in magnitude with decreasing pH. These results indicate that rhamnolipids are effective natural surfactants that may be able to replace synthetic surfactants in certain commercial applications.

Formulation and stabilization of oil-in-water nanoemulsions using a saponins-rich extract from argan oil press-cake

“…S1b). These observations were in accordance with previous studies that indicated a reduction in droplet size with increasing the intensity or duration of disruptive forces generated by the homogenizer (Bai & McClements, 2016;Qian & McClements, 2011). In addition, the particle size distributions at these homogenization conditions were monomodal with an average span value of 1.35 (Fig.…”

Eco-Friendly Synthesis of Silver Nanoparticles by Using Green Method: Improved Interaction and Application in Vitro and in Vivo.

“…Also high inhibition zone of synthesized nanoparticles against pathogenic bacteria observed at the same concentration of rhaminolipid and relatively low surfactant concentration was required to produce small droplets of AgNPs. This result were similar with that found by Bai (4). The intensity of the SPR bands increased and shifted to wavelength (500 nm) when the concentration of the rhaminolipid increased from (4 to 6×10 -3 w/v), (Fig.8).…”

Renewable Surfactants for Biochemical Applications and Nanotechnology

“…Nanoemulsions based on alkyl ether citrates, ethoxylated fatty ethers, or fatty esters of sugars (Inoh et al, 2004) were patented for a use in cosmetic formulations (Simonnet et al, 2002a(Simonnet et al, , 2002b. RL are also described as effective natural surfactant for the formation of O/W nanoemulsions that can be used for personal care formulations (Bai and McClements, 2016). Nanoemulsions can be applied for the delivery of fragrant or for the extension of the fragrance effect in personal care products, while avoiding the use of alcohol in formulations.…”