Synthesis of cellulose–silica nanocomposites by in situ biomineralization during fermentation

Bacteria cellulose (BC) generated by Acetobacter xylinum is made up of three-dimensional network of ribbon-shaped nanofibers and serves as a promising matrix for composite materials. Lately different types of nanoparticles have been adopted to modify BC via chemical reactions or physical adsorption, which usually require two steps or more and could not modify BC homogeneously. In this study we provide a one-step in situ biomineralization method during microbial fermentation to produce BC–silica nanocomposites with control over silica content. By statically culturing Acetobacter xylinum in the medium containing various amounts of sodium silicate, the slightly acidic culture environment due to consumption of glucose during fermentation could transfer sodium silicate to amorphous silica deposition that is evenly distributed on BC. The BC–silica nanocomposites obtained by this method possess superior mechanical properties such as high tensile strength and Young’s modulus, which are potential candidates for future biomedical applications. With the analysis of elemental abundance and chemical structures, we propose the synthetic mechanism of in situ production of BC–silica nanocomposites. This method is an efficient, controllable and environmental-friendly method to synthesize BC–silica nanocomposites, which also provides insights to other BC-inorganic hybrid composites and microbial modifications by microbial synthetic systems.