Production and characterization of nanoparticle induced bacterial cellulose using komagataeibacter rhaeticus

Bacterial cellulose (BC) is used in many different applications in the field of biotechnology, especially in healthcare and tissue engineering, due to its high purity, high crystallinity, water holding capacity, tensile strength and ability to adapt on a large scale. At the same time, important properties such as antibacterial activity can be added with additives. In this study, the optimum temperature, pH, inoculum concentration and incubation time values for bio-cellulose production using Komagataeibacter rhaeticus K23 were determined using Taguchi method. The experiments revealed that the optimal parameters for maximum BC production were a temperature of 32 °C, pH 5.5, an inoculum concentration of 8 log CFU·mL−1, and an incubation period of 14 days. Among these parameters, the inoculum concentration was identified as the factor most influencing BC yield. Therefore, different inoculum concentrations (8.5, 9, 9.5, 10, and 10.5 log CFU·mL−1) were tested, and an inoculum value of 8 log CFU·mL−1 resulted in significantly higher BC yield compared to other concentrations (p < 0.002). Additionally, 14-day incubation period yielded significantly higher BC production compared to other incubation periods, which were 7, 9, 11, 13, 15, 16, 17, 21, and 28 days (p < 0.001). In addition, it was investigated whether the optimized BC production by Komagataeibacter rhaeticus would gain antimicrobial properties by incorporating synthesized zinc oxide (ZnO) nanoparticles and its effects on properties such as crystallinity, water-holding capacity, thermal, and mechanical behavior. BC-ZnO nanocomposite materials were obtained by immersing BC membranes in a 1% zinc oxide solution. Subsequently, the immersed membranes were dried at 37 °C for 24 hours. The antibacterial property of the nanocomposite material was tested against Gram-positive and Gram-negative bacterial strains (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, and Bacillus subtilis RSKK 388) and showed antibacterial activity against all tested strains. Additionally, the produced BC-ZnO nanocomposites were characterized in terms of XRD, SEM, FTIR, DSC, TGA, water-holding capacity, and mechanical properties. XRD results revealed the hexagonal wurtzite structure of ZnO nanoparticles, while SEM results indicated their homogeneous distribution. The addition of ZnO nanoparticles significantly increased the thermal stability and mechanical strength of the BC membrane (p < 0.05) and conferred antibacterial activity. However, the Young's modulus decreased significantly for the BC-ZnO nanocomposite (p = 0.000). The water-holding capacity of the BC-ZnO nanocomposite was found to be similar to that of BC (p > 0.05). This study presents an important and innovative approach to synthesizing BC-ZnO nanocomposites as functional and more stable biomaterials.