A comparative analysis of biomass and lipid content in five Tribonema sp. strains at autotrophic, heterotrophic and mixotrophic cultivation

Microalgae Tribonema sp. is the first reported filamentous strain which has capability to accumulate large amounts of lipid, especially triacylglycerols (TAGs), useful for biodiesel production. In this study, five filamentous strains identified as Tribonema sp. were cultured with different carbon source and nitrogen source in batch cultures, and their biomass and total lipid contents were determined. In terms of high biomass and lipid contents, strains EA903 and EA904 were further cultivated in scale up cultures at photoautotrophic (CO2 as the carbon source), heterotrophic (glucose as the carbon source, NaNO3 and peptone as the nitrogen source, respectively) and mixotrophic (heterotrophic + light) conditions. Results suggested that autotrophic and glucose-treated cultures of Tribonema sp. strains (both EA903 and EA904) showed an evident difference on the biomass concentrations. Moreover, in spite of being characterized by higher biomass concentrations, strains EA903 and EA904 grown in heterotrophic cultivation with addition of peptone yielded lower lipid contents than those in autotrophic and heterotrophic cultivation with addition of NaNO3. The highest lipid productivity was achieved at the mixotrophic cultivation with NaNO3 addition.