Microemulsions as Potential Carriers of Nisin: Effect of Composition on Structure and Efficacy

Abstract

Water-in-oil (W/O) microemulsions based on either refined olive oil (ROO) or sunflower oil (SO), distilled monoglycerides (DMG), and ethanol were used as nisin carriers in order to ensure its effectiveness as a biopreservative. This work presents experimental evidence on the effects of ethanol concentration, hydration, the nature of oil, and the addition of nisin on the nanostructure of the proposed inverse microemulsions as revealed by electrical conductivity measurements, dynamic light scattering (DLS), small angle X-ray scattering (SAXS), and electron paramagnetic resonance (EPR) spectroscopy. Modeling of representative SAXS profiles was applied to gain further insight into the effects of ethanol and solubilized water content on the inverse swollen micelles' size and morphology. With increasing ethanol content, the overall size of the inverse micelles decreased, whereas hydration resulted in an increase in the micellar size due to the penetration of water into the hydrophilic core of the inverse swollen micelles (hydration-induced swelling behavior). The dynamic properties of the surfactant monolayer were also affected by the nature of the used vegetable oil, the ethanol content, and the presence of the bioactive molecule, as evidenced by EPR spin probing experiments. According to simulation on the experimental spectra, two populations of spin probes at different polarities were revealed. The antimicrobial effect of the encapsulated nisin was evaluated using the well diffusion assay (WDA) technique against Lactococccus lactis. It was found that this encapsulated bacteriocin induced an inhibition of the microorganism growth. The effect was more pronounced at higher ethanol concentrations, but no significant difference was observed between the two used vegetable oils (ROO and SO).

Formulation and Structural Study of a Biocompatible Water-in-Oil Microemulsion as an Appropriate Enzyme Carrier: The Model Case of Horseradish Peroxidase

“…They can both be estimated by DLS, a fast, simple, and noninvasive technique. This method not only provides information about the size and the uniformity of the dispersed phase of a system but also can help estimating the effect of an encapsulated additive on the structure, as well as determine its localization in the nanodroplets . In the present study, the term additive refers to the macromolecule of HRP.…”

“…This method not only provides information about the size and the uniformity of the dispersed phase of a system but also can help estimating the effect of an encapsulated additive on the structure, as well as determine its localization in the nanodroplets. 41 In the present study, the term additive refers to the macromolecule of HRP. The chosen biocompatible w/o microemulsion (point A, Figure 1) presents a hydrodynamic diameter of approximately 40 nm and a polydispersity index of 0.30 ± 0.03.…”

Reverse Micelles As Antioxidant Carriers: An Experimental and Molecular Dynamics Study

“…Data collection and analysis were performed using the Bruker WinEPR acquisition and processing program. Experimental results were analyzed in terms of rotational correlation time (τ R ) and order parameter ( S ) of the amphiphilic spin probes 5-DSA and 16-DSA as described elsewhere. , Probes were initially solubilized in ethanol at specific concentrations. Following this, the appropriate amounts of these solutions were transferred in test tubes and ethanol was evaporated.…”

Biocompatible Solvents and Ionic Liquid-Based Surfactants as Sustainable Components to Formulate Environmentally Friendly Organized Systems

“…RMs are based on ROO or sunflower oil (SO), distilled monoglycerides (DMG), and ethanol as a carrier of bioactive nisin [ 85 ]. Nisin is a well-known FDA-approved bacteriocin produced by lactic acid bacteria and used in the food industry as a natural bio preservative against food-borne pathogens.…”