LAUSR

On the basis of multiple single‐factor studies, the best conditions for each factor were selected by comparison. Taking the biomass, polysaccharide and protein yields of chlorella as response values, the four‐factor and three‐level response surface design experiment was performed on four parameters that significantly affected the response values to further determine the optimal conditions. The optimal parameters of the culture process were nitrogen source (urea), carbon source (sodium carbonate), nitrogen concentration (15.80 mmol/L), carbon concentration (0.36 mmol/L), phosphorus concentration (0.2 mmol/L), magnesium concentration (0.33 mmol/L), calcium concentration (0.25 mmol/L), iron concentration (0.02 mmol/L), initial pH (7.0), inoculation amount (6%) and ventilation capacity (40 L/hr). According to this process, the biomass, polysaccharide and protein yield of Chlorella sorokiniana obtained from indoor culture were close to the predicted value, which were more than three times as much as before, reaching 3.58, 0.52 and 0.46 g/L respectively. Chlorella sorokiniana, which was cultured outdoor according to the optimized process, increased its biomass, polysaccharide and protein yield by more than 1.5 times. Chlorella sorokiniana was significantly different before and after optimized culture. This provides a good source for the research of polysaccharide and protein of C. sorokiniana and helps the further study of its structure and biological activity, which makes the further development of its function more possible.