Density Functional Theory Calculations, Antibiofilm Properties, and Edible Coating Application of Kefiran for...

This study investigates kefiran's electronic properties using Density Functional Theory (DFT) at the B97-D3/def2-SVP//ωB97X-D4/def2-TZVP level, its antibiofilm activity against Staphylococcus epidermidis ATCC 35984, and its application as a coating agent for strawberries. Nuclear Magnetic Resonance (¹H and ¹³C NMR) analysis confirmed the purity of kefiran extracted from milk kefir grains. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) revealed characteristic absorption bands of carbohydrate chemical bonds. Additionally, ATR-FTIR and NMR confirmed the presence of hydroxylated glycosidic linkages and branching typical of kefiran. DFT calculations further supported this by highlighting the electronic distribution around oxygen atoms, which are responsible for hydrogen bonding and interaction potential. Experimental FT-IR bands were compared with 386 theoretical vibrational modes, showing good agreement. MEP surface highlighted reactive regions, while the 11.70 eV energy gap suggests low molecular reactivity. Antibiofilm tests showed that kefiran eradicated 35.5 % of the biofilm formed by S. epidermidis ATCC 35984 at a concentration of 512 mg/L. In antifungal tests with Fusarium solani, F. oxysporum, and Alternaria alternata, kefiran did not inhibit fungal growth but affected hyphal coloration and morphology. As a coating, kefiran reduced strawberry weight loss and spoilage, while enhancing its physicochemical stability, thereby extending shelf life.