These thick and well arranged fibrils resulted in improved mechanical strength for BC1, BC2 and BC3 relative to BC0, with the highest mechanical strength being observed for BC1. These findings are interesting because the fibril size of BC1 was not the thickest and its density was lower than that of BC2 and BC3. However, the fibrils of BC1 were more uniformly arranged than those of BC0, BC2 and BC3. This good arrangement results in a uniform response to the applied force, and could therefore increase the mechanical strength of BC1.