Presentation Breeding of alkenones producing haptophyte using heavy ion-beam irradiation

H, Araie  ,  長谷, 純宏  ,  大野, 豊  ,  I, Suzuki  ,  Y, Shiraiwa

Biofuel production using algae is attracting keen attention as a next generation energy candidate because it has advantages such that production per unit area is higher than land plants and not competing with food production. However, in order to advance the algae biomass industry, it is necessary to improve oil-producing algae by mutation for making oil high accumulated strain or strain with high growth rate, and so on. In this research, we focused on unique lipid called alkenones that are synthesized by only five marine haptophyte species since that are thought as one of the sources of fossil fuels. We selected one of alkenone-producing haptophytes, Tisochrysis lutea, as material to achieve efficient alkenone production. For the purpose, we have developed heavy ion-beam irradiation technology since obtained mutants can be used in open system as non-GMO. Heavy ion-beam irradiation was performed on T. lutea (T-Iso strain) placed on the agar plate with 0~320 Gy of carbon ions (26.7 MeV/u) at the TIARA ion beam irradiation facility, Japan. After 1~2 week, we counted the number of colonies for survival rate and picked up colonies for evaluation of alkenone productivity. Dose response curve showed that LD50 of the colony formation was around 30 Gy but no survival over 120 Gy. Seven of 32 strains at 80 Gy irradiation and 21 of 59 strains at 20 Gy irradiation showed approximately 1.5-fold higher alkenone productivity than wild type. These results suggested that irradiation dose at around LD50 is suitable for obtaining useful mutants. This is the first attempt to improve alkenone productivity by using heavy ion-beam irradiation.

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