Outdoor Cultivation of Marine Diatoms for Year-Round Production of Biofuels.

Biofuel production using microalgae is believed to have the advantage of continuous year-round production over crop plants, which have strong seasonality. However, actual year-round production of microalgal lipids using outdoor mass cultivation has rarely been demonstrated. In our previous study, it was demonstrated that the oleaginous diatom, , was culturable in outdoor bioreactors from spring to autumn, whereas biomass and lipid production in winter failed because did not grow below 15 °C. Therefore, another candidate strain that is culturable in winter is required. In this study, a cold-tolerant diatom, sp. JPCC CTDA0820, was selected as a promising candidate for biofuel production in winter. Laboratory-scale characterization revealed that this diatom was culturable at temperatures as low as 10 °C. Subsequently, (April-October) and sp. JPCC CTDA0820 (November-March) were cultured in outdoor open-pond bioreactors, wherein year-round production of diatom lipids was successfully demonstrated. The maximal values of areal productivities of biomass and lipids reached to 9.79 and 1.80 g/(m² day) for , and 8.62 and 0.92 g/(m² day) for sp. JPCC CTDA0820, respectively. With the combined use of these two diatom species, stable year-round production of microalgal lipids became possible.