Abstract

Platymonas subcordiformis, a model microalga in microalgal biotechnology, is rich in bioactive substances such as fatty acid, protein and vitamin, and hence it has been widely applied in biofuel, environmental purification, and pharmaceutical industry. In the current study, promotion effects of nitrogen on cell proliferation of P. subcordiformis were investigated by using spectrophotography ana-lysis and cytometry analysis, and the correlation between optical density at wavelength of 680 nm (OD₆₈₀) and cell density was estimated. The results show that there were significant effects of nitrogen on the growth ofP. subcordiformis, with the OD₆₈₀, cell density and dry weight increasing with the increase of nitrogen concentration. In the termination of experiment, OD₆₈₀ values were 0.037, 0.111, 0.188, 0.393, 0.551 and 0.628; cell densities were 4×10⁴, 2.6×10⁵, 4.1×10⁵, 8.3×10⁵, 1.15×10⁶ and 1.38×10⁶ cells/mL; and dry weights were 0.021 7, 0.088 3, 0.131 7, 0.177 5, 0.238 3 and 0.310 0 g/L at the nitrogen concentrations of 0, 7.5, 15, 37.5, 75 and 150 mg/L, respectively. In addition, there was significantly positive correlation between OD₆₈₀ and cell density throughout the experiment, with the regression equation of cell density (10⁴ cells/mL) = 218.05OD₆₈₀ - 1.6014 (R² = 0.997 1) on day 11. The findings suggest that nitrogen promotes the cell growth and proliferation of P. subcordiformis, and that spectrophotography analysis is relatively simple, quick and accurate, which can be used in the scientific research or industrialization of this microalga.

Key words: Spectrophotography analysis, cytometry analysis, cell proliferation,Platymonas subcordiformis, nitrogen