Exopolysaccharide from Bacillus vallismortis WF4 as an emulsifier for antifungal and antipruritic peppermint oil emulsion.

ABSTRACT

The paper aims to study emulsifying capacities of bacterial exopolysaccharides (EPS) on essential oils (EOs), and the antifungal and antipruritic properties of the emulsion. A marine bacterium Bacillus vallismortis was identified and named the WF4 strain. The molecular weight of the EPS was 3.83 × 105 Da. The composition of monosaccharide was mannose/glucose/xylose/arabinose (51.77%20.82%13.28%14.13%). Rheology study shows shear thinning characteristics. EPS had significant emulsifying activity to EOs at 1.0% (w/v). The prepared EPS-peppermint oil (EPS-PO) emulsion was an O/W emulsion with an average particle size of 16.3 µm and was stable. The antifungal activity results showed that the minimum inhibitory concentration (MIC) of the EPS-PO emulsion was 4.0 mg/mL, and the pure PO was 16.0 mg/mL, indicating that the emulsion of PO could enhance the antifungal ability. Moreover, propidium iodide (PI) staining and Scanning electron microscopy (SEM) observation showed that the EPS-PO emulsion damaged the membrane of Candida albicans (CA). The anti-itching test showed that the EPS-PO emulsion could significantly increase the itch threshold of guinea pigs to phosphate histamine and reduce the number of scratching incidents. This study laid the foundation for the application of EPS as an emulsifier and highlighted the application prospects of EPS in topical emulsion.