Abstract: This study optimized the extraction process of Chlorella protein using response surface methodology and characterized its secondary structure. With the protein solubility rate of Chlorella as the indicator, the effects of ultrasonic power, ultrasonic time, NaOH mass fraction, and water bath time on the extraction rate were investigated. Based on the Plackett-Burman design, a four-factor three-level response surface analysis was conducted to determine the extraction process of Chlorella protein. The results showed that the optimal extraction conditions for Chlorella protein were ultrasonic power of 460.08 W, ultrasonic time of 16.05 min, NaOH mass fraction of 14.03%, and water bath time of 37.18 min, with a solubility rate of 87.64%. The extracted Chlorella protein was purified using isoelectric focusing under optimal conditions and then subjected to FTIR analysis, microscopic structure analysis, and amino acid analysis. The results indicated that the secondary structure of Chlorella protein mainly consisted of β-sheet, accounting for 30.00% of the total content. The microscopic structure revealed a smooth surface with pore structures, and it contained five essential amino acids, accounting for 42.71% of the total content. In conclusion, the ultrasonic-assisted alkaline method demonstrates significantly improved protein wall-breaking efficiency and high protein extraction rate for Chlorella, with simple operation and low cost. It has promising prospects for industrial applications and provides relevant references for the food application of Chlorella protein.
Key words: Chlorella breaks the wall; protein dissolution process; ultrasonic treatment; alkaline crushing; amino acid
（Acta Laser Biology Sinica, 2024, 33(4): 347-356）