This study investigated the induction of oil synthesis in the oleaginous diatom, Fistulifera solaris, following irradiation with small doses of UV-C. A rapid induction of oil accumulation was confirmed within 6 h following UV-C radiation of the diatom cells, with increases in cell oil body volumes after 24 h of approximately 4- to 6-fold from the initial volume. Reactive oxygen species (ROS), which can be generated by a UV-C-mediated reaction, were detected in irradiated cells and the correlation between ROS generation and oil accumulation was confirmed. The smallest UV-C intensity required for oil induction in the cells was 10 mJ/cm(2). Based on the ideal biodiesel profile, the most suitable FAME composition was obtained when UV255 was used to irradiate the cells. The UV-C radiation method is therefore a solution for shortening the oil accumulation period and improving biodiesel productivity. (C) 2017 Elsevier Ltd. All rights reserved.