Antibacterial Activity of Biocellulose with Oregano Essential Oil against Cronobacter Strains

Biocellulose, named "the biomaterial of the future", is a natural and ecologically friendly polymer, produced by selected acetic acid bacteria strains. Biocellulose impregnated with antimicrobial agents can be used as a novel, safe, and biodegradable food packaging material, helping extend the shelf life of some products and may also have the chance to replace typical plastic packaging, which is a big environmental problem these days. This study aimed to evaluate if cellulose impregned with natural oregano essential oil could show antibacterial activity against Cronobacter strains, which can occur in food, causing diseases and food poisoning. Bacterial cellulose was obtained from two acetic bacteria strains, Gluconacetobacter hansenii ATCC 23769 and Komagataeibacter sp. GH1. Antibacterial activity was studied by the disc-diffusion method against chosen Cronobacter strains, isolated from the plant matrix. Oregano essential oil has been shown to penetrate into the structure of bacterial cellulose, and after applying cellulose to the solid medium, it showed the ability to migrate. Biopolymer from the strain K. sp. GH1 was able to better absorb and retain essential oregano oil (OEO) compared to bacterial cellulose (BC) produced by the G. hansenii ATCC 23769. Bacterial cellulose with oregano essential oil from strain Komagataeibacter GH1 showed generally greater inhibitory properties for the growth of tested strains than its equivalent obtained from G. hansenii. This was probably due to the arrangement of the polymer fibers and its final thickness. The largest zone of inhibition of strain growth was observed in relation to C. condimenti s37 (32.75 mm ± 2.8). At the same time, the control sample using filter paper showed an inhibition zone of 36.0 mm ± 0.7. A similar inhibition zone (28.33 mm ± 2.6) was observed for the C. malonaticus lv31 strain, while the zone in the control sample was 27.1 mm ± 0.7. Based on this study, it was concluded that bacterial cellulose impregnated with oregano essential oil has strong and moderate antimicrobial activity against all presented strains of the genus Cronobacter isolated from plant matrix. Obtained results give a strong impulse to use this biopolymer as ecological food packaging in the near future.

Keywords: Cronobacter; antibacterial activity; biocellulose; food packaging; oregano essential oil.