干酪乳清酶解产物抗氧化肽的分离和纯化

干酪乳清Alcalase 2.4L酶解的最优条件，即酶解时间为2 h、pH 9.5、酶与底物比为4%、酶解温度为50 ℃。利用超滤、葡聚糖凝胶层析和三羟甲基氨基甘氨酸-十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（tricine-sodiumdodecyl sulfate-polyacrylamide gelelectrophoresis，tricine SDS-PAGE）等方法从干酪乳清中提取抗氧化性蛋白肽。分别考察操作压力、料液温度、料液pH值、操作时间对超滤膜膜通量的影响。乳清酶解物超滤的最佳条件为：压力0.25 MPa、温度30 ℃、时间120 min、初始pH 9.0。分子质量4 000～6 000 D肽的水解液脂质过氧化抑制率最高，达到47.28%。利用Sephadex G-50型葡聚糖凝胶进行纯化，将分离的组分进行Tricine-SDS-PAGE分析和脂质过氧化抑制率的测定。第34管洗脱液的脂质过氧化抑制率最高，分子质量范围为4 000～4 100 D。

Isolation and Purification of Antioxidant Peptide from Cheese Whey Hydrolysates Produced with Alkaline Protease

Cheese whey hydrolysates were obtained by enzymatic hydrolysis with an alkaline protease “alcalase” for 2 h
at 50 ℃ and an initial pH of 9.5 with an [E]/[S] ratio of 4%. The antioxidant peptide was purified from cheese whey
hydrolysates by ultrafiltration, polydextran gel chromatography and tricine-sodium dodecyl sulfate-polyacrylamide
gelelectrophoresis (tricine SDS-PAGE). The optimal operating pressure, hydrolysate temperature and pH and ultrafiltration
time for the improved ultrafiltration membrane flux were found to be 0.25 MPa, 30 ℃, 9.0 and 120 min, respectively. The
peptide with molecular weights ranging from 4 000 to 6 000 D had the highest inhibitory activity on lipid peroxidation, with
an inhibitory rate of approximately 47.28%. After purification with Sephadex G-50, the separated fractions were determined
by tricine SDS-PAGE and lipid peroxidation inhibition, respectively. Fraction 34 with molecular weight distribution ranging
from 4 000 to 4 100 D had the highest inhibitory activity on lipid peroxidation.