咸鸭蛋清胃蛋白酶水解产物的抗菌性及抗氧化性

Antibacterial and antioxidant activities of pepsin hydrolysatefrom salted duck egg white

摘要:

【目的】提高对咸鸭蛋清的综合利用，制备具有生物活性的蛋白水解产物。【方法】采用超滤对咸鸭蛋清进行脱盐及分级，利用胃蛋白酶对不同分子量范围的咸鸭蛋清蛋白组分进行酶解，并对不同组分的水解产物进行体外抑菌试验，测定其最低抑菌浓度(MIC)、最低杀菌浓度(MBC)、细菌细胞膜完整性及抗氧化活性。【结果】超滤后得到3种不同分子量的组分，组分A (Mw>50 kDa)、组分B (50 kDa>Mw>20 kDa)和组分C (20 kDa>Mw>5 kDa)。其中，组分A和组分B的水解产物对大肠杆菌的生长有抑制作用。2种组分的MIC分别为1 024 μg/mL和2 048 μg/mL，MBC均为2 048 μg/mL。大肠杆菌进入稳定期OD₆₀₀值约为1.15，添加2种水解产物浓度达1×MIC时，OD₆₀₀值降至0.79和0.86，浓度达2×MIC时，OD₆₀₀值降至0.50和0.68。2种水解产物可破坏大肠杆菌细胞膜，达到较好的抑菌效果。而金黄色葡萄球菌对3种水解产物均不敏感，抑菌效果较差。另外，3种水解产物均具有抗氧化活性，它们对DPPH自由基清除能力分别达0.5倍Trolox (水溶性维生素E)、0.67倍Trolox、0.38倍Trolox。【结论】超滤可同时实现咸蛋清脱盐及富集不同目标蛋白的目的。目标蛋白酶解组分具备抗菌活性和抗氧化活性，同时可作为一种营养添加剂，提高了咸鸭蛋清的附加价值和利用率。

Abstract:

[Objective] To improve the comprehensive utilization of salted duck egg white, bioactive proteolytic products were prepared. [Methods] In this study, salted duck egg white wasdesalted and graded by ultrafiltration. The protein fractions of salted duck egg white within different molecular weight ranges were hydrolyzed by pepsin. The bacterial inhibition and antioxidant activitiesofthe hydrolysates were determined in vitro, including the determination of minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and cell membrane integrity. [Results] Three fractions of different molecular weights were obtained from salted duck egg white by ultrafiltration, which were fraction A with Mw>50 kDa, fraction B with 50 kDa>Mw>20 kDa and fraction C with 20 kDa>Mw>5 kDa. Among them, the hydrolysates of fractions A and B had inhibitory effects on the growth of Escherichia coli. The MICs of the two fractions were 1 024 μg/mL and 2 048 μg/mL, respectively, and the MBCs were both 2 048 μg/mL. The OD₆₀₀ value of E. coli was about 1.15 after entering the stationary phase. When the hydrolytic peptide was added at a concentration of 1×MIC, the OD₆₀₀ values of the bacterial solution in stationary phase decreased to 0.79 (A) and 0.86 (B), respectively. When the hydrolytic peptide was added at a concentration of 2×MIC, the OD₆₀₀ values decreased to 0.5 (A) and 0.68 (B), respectively. The two hydrolysates had good antibacterial effects, which were attributed to the destruction of E. coli cell membrane. However, Staphylococcus aureus was not sensitive to all three hydrolysates, and the inhibitory effect was poor. Moreover, the hydrolysates of fractions A, B and C all had antioxidant activities, and their scavenging ability against DPPH radicals reached 0.50, 0.67 and 0.38 times Trolox, respectively. [Conclusion] The salted duck egg white could be simultaneously desalted and enriched to obtain different target proteins by ultrafiltration. The hydrolysates of the obtained target proteins possessed antibacterial and antioxidant activities, and could be used as nutritional additives, which improved the added value and utilization of salted duck egg white.