Mixotrophic growth of Chlorella sorokiniana in outdoor enclosed photobioreactor

Chlorella sorokiniana was cultured in heterotrophic or mixotrophic mode in outdoor enclosed tubular photobioreactor. The culture temperature was maintained at 32-35 degrees C. At night, the Chlorella culture grew heterotrophically, and 0.1 M glucose was completely consumed. The biomass growth yield of glucose was 0.35 +/- 0.001 g-biomass g-glucose(-1). During the day, the algal culture grew mixotrophically and the biomass growth yield was 0.49 g-biomass g-glucose(-1) in low density culture (initial biomass concentration, X(0) = 2 g 1(-1)), 0.56 g-biomass g-glucose(-1) in medium density culture (X(0) = 4 g 1(-1)) and 0.46 g-biomass g-glucose(-1) in high density culture (X(0) = 7 g 1(-1)). The daily area productivity of the culture, with X(0) = 4 g 1(-1), corresponded to 127 g-biomass m(-2) d(-1) during the day and 79 g-biomass m(-2) d(-1) during the night. In all the cultures, the dissolved O-2 concentration increased in the morning, reached the maximum value at noon, and then decreased in the afternoon. The dissolved CO2 concentration remained at 3 mBar in the morning and increased in the afternoon. Glycolate was not found to accumulate in culture medium.