[Effects of glucose on photosynthesis and growth of Chloralla sp. HN08 cells].

Objective: To study the potential of using glucose as carbon source to produce microalgae biomass and biochemical components, such as photosynthetic pigments, lipids, carbohydrates and proteins by tropical marine microalgae Chloralla sp. HN08.

Methods: We compared the growth characteristics of Chloralla sp. HN08 cells under photoautotrophic and mixotrophic (10 g/L glucose was added into the medium) conditions. The photosynthesis, specific growth rates, cell densities, and the content of cell's major components including lipids, starch, soluble sugar, and soluble protein were determined and compared.

Results: Glucose (10 g/L in medium) could promote Chlorella growth and increase the final cell density under light condition. However, cells declined gradually under heterotrophic condition. Under mixotrophic condition, the specific growth rate and the final cell density were 6.8 and 1.3 times as that of cells under photoautotrophic condition, respectively. The content of soluble sugar, starch, and lipids in mixotrophic cells was also significantly higher (P<0.05) than that in photoautotrophic cells. However, the content of soluble protein and photosynthetic pigments of mixotrophic cells was significantly lower (P<0.05) than that of autotrophic cells. Algae culture with glucose addition showed a higher light saturation as well as respiration rate. No significant difference in net photosynthesis rate was found between autotrophic and mixotrophic cultures (P>0.05).

Conclusion: Under light condition, glucose as a carbon source can promote lipids and starch accumulation, as well as biomass production.