Optimization of Trophic Modes for Enhancing the Production of Biomass, Protein, and Chlorophyll from Chlorella pyrenoidosa
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Abstract:
The biomass of Chlorella pyrenoidosa and its cellular protein and chlorophyll contents were enhanced by optimizing trophic modes and culture conditions. The results showed that glucose concentration could significantly influence the biomass concentration of C. pyrenoidosa under mixotrophic and heterotrophic conditions (p<0.05), but no significant effect was found with different nitrate concentrations. The highest biomass concentration (21.31 g/L) was obtained when C. pyrenoidosa was cultivated in heterotrophic culture for four days with medium containing 50 g/L glucose and 3.75 g/L nitrate, and was significantly higher than the highest biomass concentration obtained in mixotrophic culture (14.32 g/L) with a salinity of 15‰ (p<0.05). After glucose depletion, the heterotrophic C. pyrenoidosa strain was diluted with a nitrate-containing medium without glucose for photon-induced cultivation, and the concentration of nitrate was optimized. The results showed that 48-hour photon-induced cultivation under a low light intensity (6,411±532 Lux) in a medium containing 3.75 g/L nitrate produced high contents of protein (54.1%) and chlorophyll (3.14%) in C. pyrenoidosa; these values were increased by 207.74% and 342.25%, respectively, compared with those obtained before photon-induced cultivation. Additionally, the yields of protein and chlorophyll reached 1.32 g/(L?d) and 0.09 g/(L?d), respectively, significantly higher than the peak values from mixotrophic or heterotrophic culture (p<0.05).
