Culture at 8 days (a - Top), and 23 days (b - bottom). The green indicates oil droplets where TAGs have accumulated, while the red indicates thylakoid membranes. TAG accumulation can be observed under two nutrient stress conditions. Thylakoid membranes can be observed even at 23 days under phosphorus starvation conditions (Right).

Culture at 8 days (a – Top), and 23 days (b – bottom). The green indicates oil droplets where TAGs have accumulated, while the red indicates thylakoid membranes. TAG accumulation can be observed under two nutrient stress conditions. Thylakoid membranes can be observed even at 23 days under phosphorus starvation conditions (Right).

Two scientists at the Tokyo Institute of Technology have enhanced the lipid accumulation function in nutrient-starved algae, maintaining the cell growth through photosynthesis. Masako Iwai, Core Research for Evolutional Science and Technology (CREST) researcher and member at the Center for Biological Resources and Informatics; and Professor Hiroyuki Ohta, of the Earth-Life Science Institute and Center for Biological Resources and Informatics realized this development by a gene transformation using a phosphorus starvation-inducible promoter. The scientists say that this result represents a big advance for the production of bioenergy at the industrial level using algae.

Using the model algae Chlamydomonas, it was discovered that lipid accumulation in phosphorus-starved cells differed from nitrogen starved cells, which has been conventionally known. The accumulation of TAGs in phosphorus-starved cells was possible while also maintaining thylakoid membranes, where photosynthesis takes place. Focusing on genes, which expressions are increased under phosphorus starvation, a transformation system was constructed that could enhance the accumulation of lipids under phosphorus starvation conditions. It is expected that this system will be used in the future to not only enhance lipid accumulation, but also manipulate the kinds of fatty acids included in lipids.

The research was a joint effort with Mie Shimojima, assistant professor at the Tokyo Institute of Technology’s Center for Biological Resources and Informatics, and Keiko Ikeda, technical staff at the Tokyo Institute of Technology’s Biomaterial Analysis Center. The results of the research appeared in the English scientific journal “Plant Biotechnology Journal” volume 12, issue 6 on August 2014. The electronic version of the same was published on 9 June.