Factors affecting the growth and the oil accumulation of marine microalgae, Tetraselmis suecica

Biomass production and oil productivity in microalgae culture are the most important key factors for algal biodiesel production. However, proper culture condition for the biomass production of microalgae is different from that for the oil production of microalgae. A study on the biomass production of Tetraselmis suecica using various light intensities and nitrate concentrations as growth factors was carried out to evaluate proper culture conditions in 20-L batch culture. The effect of nitrate depletion on the oil accumulation was also evaluated with two-stage culture. It took 5 days to reach the stationary phase for the cultures of T. suecica on the light intensities of 108.9 and 133.1 mu mol m(-2) s(-1) with biomass of 0.89 and 0.88 g dcw L-1, respectively. Biomass productions of 1.07 and 1.00 g dcw L-1 were obtained with the nitrate concentrations of 18.6 and 24.7 mg L-1, respectively. The two-stage culture increased oil contents from 7.6 to 17.3% (w/w) and contents of C-16-C-18 fatty acids from 540.2 to 720.5 mg g(-1) oil. The predominant fatty acid was palmitic acid (C-16:0) in nitrate depletion group, however, oleic acid (C-18:1) was predominated in nitrate added groups. The two-stage culture enhanced overall oil productivity of 18.7 mg g(-1) day(-1) which is higher than that of 12.2 mg g(-1) day(-1) in single-stage culture.