We have performed a systematic study of interstellar dust grains in various environments of galaxies. AKARI has revealed the detailed properties of dust grains not only in star-forming regions but also in regions not relevant to star formation, some of which are found not to follow our old empirical knowledge. Because of its unique capabilities, AKARI has provided new knowledge on the processing of large grains and polycyclic aromatic hydrocarbons (PAHs). For example, we detect PAHs from elliptical galaxies, which show unusual spectral features and spatial distributions, demonstrating importance of material processing in the interstellar space. We find that copious amounts of large grains and PAHs are flowing out of starburst galaxies by galactic superwinds, which are being shattered and destroyed in galactic haloes. We discover evidence for graphitization of carbonaceous grains near the center of our Galaxy, providing a clue to understanding the activity of the Galactic center. We review the results obtained from our AKARI program, focusing on the processing of carbonaceous grains in various environments of galaxies.

ABSTRACT
1. INTRODUCTION
2. ORIGINS OF DUST AND PAHs IN ELLIPTICAL GALAXIES
3. STRUCTURAL CHANGES OF HYDROCARBONS IN SHOCKED REGIONS
4. GRAPHITIZATION OF DUST IN THE GALACTIC CENTER
5. SUMMARY
REFERENCES

• H. KANEDA(Graduate School of Science, Nagoya University)
• D. ISHIHARA(Graduate School of Science, Nagoya University)
• T. ONAKA(Department of Astronomy, Graduate School of Science, University of Tokyo)
• I. SAKON(Department of Astronomy, Graduate School of Science, University of Tokyo)
• T. SUZUKI(Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency)
• K. KOBATA(Graduate School of Science, Nagoya University)
• T. KONDO(Graduate School of Science, Nagoya University)
• M. YAMAGISHI(Graduate School of Science, Nagoya University)
• A. YASUDA(Graduate School of Science, Nagoya University)