Microencapsulation and Antimicrobial Activity of Plant Essential Oil Against Ralstonia solanacearum

Ralstonia solanacearum is a common plant bacterium, and the improper use of chemicals to control this bacterium is harmful to the environment. Many undeveloped aromatic plants and green plant waste can be used for the preparation of essential oils (EOs). EOs have various biological activities, such as bacteriostatic, insecticidal and anti-oxidation, and are currently in the exploration stage for the control of R. solanacearum . In the present study, the inhibitory activity of ten EOs against R. solanacearum was determined by an antibacterial test. To prolong the duration of antibacterial activity, microcapsules of EOs were prepared by the complex coacervation method, and the optimal preparation conditions were obtained by central composite design method. The results showed that cinnamon EOs had the strongest antibacterial activity. For GIM1.71, GIM1.74, GIM1.76, GMI1000 and RS-5, the EC 50 values of cinnamon EOs were 0.055 mg/mL, 0.071 mg/mL, 0.03 mg/mL, 0.067 mg/mL and 0.063 mg/mL, respectively. The preparation condition of cinnamon EOs microcapsules was as follows: the core-wall ratio was 4.35:1, the ratio of chitosan and sodium alginate was 0.15:1, and the calcium chloride concentration was 0.95 wt%. The encapsulation efficiency was 87.32%, and the average particle size of microcapsule was 870.4 μm. The release rate of microcapsule was 44.53% at 100 °C for 6 h and the release of the core materials in microcapsules was in line with Korsmeyer–Peppas release kinetics. Microcapsules placed at room temperature for 7 days still had significant antibacterial activity against five species of R. solanacearum . Due to its good stability and antibacterial activity, cinnamon EOs microcapsules will have great market application prospects as antibacterial agents. Graphic Abstract