Growth and Oil-production Characteristics of Eustigmatos vischeri Hibberd under Different Cultivation Modes

We investigated the biological characteristics of the alga Eustigmatos vischeri Hibberd, and explored the effects of four cultivation modes (batch, two-stage, fed-batch and bicarbonate-addition culture) on its growth and lipid accumulation. We cultured E. vischeri by supplying different initial sodium nitrate, which was replaced with fresh medium, with a small amount of sodium nitrate and low concentrations of sodium bicarbonate or ammonium bicarbonate added. The biomass concentration in the batch culture reached 8.41 g/L, while the highest total lipid content was 65.16% and productivity was 0.30 g·L^-1·d^-1. Compared to the batch culture, the two-stage and fed-batch cultures had no significant effect on lipid accumulation in E. vischeri. However, the bicarbonate-addition culture did have a significant effect on growth and lipid accumulation, especially maximum biomass concentration in the NaNO₃+NH₄HCO₃ group, which reached 11.56 g/L, and total lipid content reached 60.92%. Thus, the biomass concentration and total lipid content increased by almost 1.0 g/L and 10%, respectively, compared with that in the batch culture under the same nitrogen concentration. In addition, the productivity of total lipids also increased (0.39 g·L^-1·d^-1). Our results indicated that E. vischeri is an oleaginous microalga with high development and utilization value. Moreover, the addition of a low concentration of ammonium bicarbonate promoted the growth and lipid accumulation of E. vischeri, and is thus a suitable method for cultivation.