Production of Bacterial Cellulose with Well Oriented Fibril on PDMS Substrate

Acetobacter xylinum, which is an aerobic bacterium, synthesizes bacterial cellulose (BC) with unoriented microfibril network in form of gel at the air and liquid interface (BC-air). In this work, we discovered that BC gel produced on an oxygen permeable substrate of polydimethylsiloxane (PDMS) shows strong birefringence with colorful images, indicating a liquid crystal-like structure. Furthermore, we found that uni-axially oriented BC gels can be obtained by culturing the BC on the PDMS with ridged morphology. The degree of orientation of BC gels, as revealed by the birefringence, increases with the decrease in the ridge size of the PDMS substrate. An optimum ridge size of 4.5mm was observed where the BC gels show the highest birefringence ( n), the highest fracture stress ( ), highest swelling degree (q), the lowest elastic modulus (E), and the thickest BC fibril. The optimum ridge size is related to the contour length of the bacteria cells. When the ridge size was smaller than 4.5mm, the n steeply decreased to a value comparable to that on smooth flat PDMS mold surface. The fracture stress, of the uni-axially oriented BC gel under elongation was 4.6MPa, which was 2.3 times higher than that of BC-air ( ¼2MPa).