**4. Conclusions**

Since chitin functions as an electrolyte membrane for fuel cells, it has been clarified that it is a proton conductor. It was found that the presence of water molecules is very important for the appearance of proton conductivity in chitin, and that these water molecules behave like conductors in chitin hydrate to conduct protons. Furthermore, it was suggested that the orientation dependence of the proton conductivity appearing in the oriented chitin is due to the bottleneck caused by the different hydrogen bond distances with the water molecules formed in the chitin depending on the position. It was also indicated that the high proton conductivity of oriented chitin appears by increasing the number of pathways by utilizing the bottleneck and the pathway in the fiber vertical direction, which is the low activation energy pathway. When a fuel cell using the fiber direction of oriented chitin having high proton conductivity was prepared, an improvement in proton conductivity of nearly 24 times was observed. In the future, chitin orientation methods and chemical approaches are expected to provide a foothold for more practical polysaccharide-based electrolyte membranes and to clarify new value in the energy field.
