3. Results and discussion
The absorbance at wavelength of 378 nm (OD378) of algal cells at different growth stages at 7, 14, 21, 28, 35, 50, 65, 80 and 95 days and the algal cell dry weight, observation of the microalgal growth process by extending the culture cycle: Algal cells are in a phase of growth adaptation from 0 to 14 days and grow more slowly; After entering the second phase of logarithmic growth, the growth of algal cells was more rapid, and both the absorbance OD378 and the dry weight of algal cells showed a steady upward trend, the algal cells entered the third phase of decay at 65 to 95 days, and the OD378 and the algal cell dry weight gradually declined to the demise of the algal cells.