High photosynthetic productivity of green microalga Chlorella sorokiniana

The batch culture of a newly isolated strain of a green microalga, Chlorell a sorokiniana, was carried out using a conical helical tubular photobioreac tor. The isolate was capable of good growth at 40 degrees C under an airstr eam enriched with 10% CO2. The maximum photosynthetic productivity was 34.4 g of dry biomass/(m(2) of installation area . d) (12-h light/12-h dark cyc le) when the cells were illuminated with an average photosynthetic photon f lux density (photosynthetically active radiation ([PAR] 400-700 nm) simulat ing the outdoors in central Japan (0.980 mmol photons/[m(2).s]). This corre sponded to a photosynthetic efficiency of 8.67% (PAR), which was defined as the percent age of the light energy recovered as biomass (394 kJ/[reactor. d]) to the total light energy received (4545 kJ/[reactor.d]). A similarly h igh photosynthetic efficiency (8.12% [PAR]) was also attained in the combin ed presence of 10% CO2, 100 ppm of NO, and 25 ppm of SO2. Moreover, good ph otosynthetic productivity was also obtained under high temperature and high light intensity conditions (maximum temperature, 46.5 degrees C; 1.737 mmo l photons/ [m(2).s]), when simulating the strong irradiance of the midday s ummer sun. This strain thus appears well suited for practical application f or converting CO2 present in the stack gases emitted by thermal power plant s and should be feasible even during the hot summer weather.