Bacterial cellulose/gelatin composites: in situ preparation and glutaraldehyde treatment

Bacterial cellulose (BC)/GEL composites were prepared in situ by adding gelatin into BC-producing culture medium. The addition of gelatin interfered with the formation of the BC pellicle structure and thus made the BC yield and growth rate quite different from that of pure BC. Scanning electron microscope images showed that the width of cellulose ribbons became narrower than that of pure BC and the gelatin filled in the pores of BC to form a dense structure. The addition level of gelatin significantly influences the yield of BC/GEL composites. An optimum value of 0.5 wt/v% gelatin was attained, with which the highest yield of 0.0541 g/100 mL was achieved. Under this condition, the weight percentage of gelatin in BC/GEL composite was 65 wt%. BC/GEL composites were treated with glutaraldehyde to crosslink BC fibrils and gelatin. The crosslinking degree, determined by the concentration of glutaraldehyde and crosslinking time, could affect the swelling behavior, thermal stability and mechanical properties of composites. With increasing of the crosslinking degree, the crystallinity index and swelling behavior of the composites decreased. The increase in the crosslinking degree also descreased the composite’s strain at break in elongation but increased the compressive and tensile strength. Covalent bonding between BC and gelatin provides good strength retention to the glutaraldehyde-treated composites with a high crosslinking degree. Considering the cytocompatibility and properties of composites, the most appropriate concentration of glutaraldehyde and crosslinking time were 1.0 wt/v% and 24 h, respectively.