2009 年 21 巻 2 号 p. 81-86
We are planning to develop a new food production system utilizing Euglena gracilis, a photosynthetic microalga. In our previous reports, we investigated the influences of CO2 concentrations (0.04 and 10%) and light qualities (red and blue) on its growth and nutrient contents. We found that the quantum yield of Euglena was greater than that of higher plants, and on 10% CO2 condition and red and blue (PPFD ratio = 9:1) light irradiation was optimal for the growth and contents of protein and paramylon (β-1.3 glucan), and, in contrast, the 0.04% CO2 condition and blue light irradiation was optimal regarding the contents of antioxidant vitamins. In this report, we investigated the qualities of these nutrients in Euglena compared with those in other algae (protein), yeast (vitamin). Euglena proteins were composed of large quantities of well-balanced essential amino acids, with a score of 88, and a high net protein utilization of 79.9, similar to cow-milk casein. Tryglycerides in Euglena were mainly composed of unsaturated fatty acids, especially linoleic and linolenic acids, which are essential fatty acids for humans, as well as a large amount of arachidonic acid. Euglena cells also contained higher levels of vitamins than yeast, a good vitamin source, and some minerals. Furthermore, Euglena cells accumulated paramylon. We thus concluded that Euglena cells were appropriate for use in new food source systems.