Investigation of the effects of bacterial cellulose–silver nanoparticle composite on Staphylococcus aureus biofilm formation

In this thesis study, the effects of bacterial cellulose (BC), a biocompatible biopolymer, combined with biologically synthesized silver nanoparticles (AgNPs), on Staphylococcus aureus biofilm formation were investigated. Celluloseproducing bacterial isolates were obtained from kombucha and traditional vinegar samples and screened based on their cellulose production potential. The isolate with the highest yield Komagataeibacter europaeus strain BS1: PV687455.1 was used to prepare the composite matrix, while AgNPs were synthesized most efficiently by isolate Komagataeibacter sp. strain NP1: PV687535.1 using an eco-friendly green synthesis method. Notably, both strains belong to the same genus, Komagataeibacter, highlighting its dual functional potential in providing both a structural biopolymer and a reducing agent for nanoparticle synthesis. The synthesized AgNPs were characterized by UV–Vis, FESEM, EDX, and FT–IR analyses. Homogeneous incorporation of AgNPs into the BC matrix resulted in BC–AgNP composite films, whose surface morphology and chemical structure were examined in detail. Antibacterial tests (disk diffusion, well diffusion, and growth curve) revealed that BC–AgNP films produced larger inhibition zones and provided prolonged antimicrobial effects compared to free AgNPs. In addition, crystal violet and resazurin assays revealed that these films inhibited biofilm formation by 98.10% and reduced metabolic activity by up to 125%, based on resazurin non-reduction. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined to be 0.2 µg/mL and 1.9 µg/mL, respectively, indicating that the BS–AgNP composites exhibited strong antibacterial and antibiofilm activities even at low concentrations. KEYWORDS: Bacterial cellulose, silver nanoparticles, composite film, antibacterial activity, biofilm, Staphylococcus aureus