α-半乳糖苷酶的固定化及其对豆浆中低聚糖的水解

Immobilization of α-galactosidase and hydrolysis of oligosaccharides in soybean milk

α-半乳糖苷酶是解决大豆制品食物不耐受的关键酶,但其活性不高、耐热性较差。文章使用海藻酸钠和壳聚糖2种固定化载体,研究了固定化后的α-半乳糖苷酶的最适p H、温度及水解大豆低聚糖的最适酶底比和重复使用效果。实验结果表明,游离酶的最适p H为4.0,最适温度为50℃,水解8.0 h时的大豆低聚糖水解率为79.28%,添加量为5 U/20 m L时,大豆低聚糖的水解率为51.88%;海藻酸钠固定化酶的最适p H为7.0,温度为45℃,保存52 d后相对酶活为(88.10±0.0029)%,水解8.0 h后大豆低聚糖的水解率达到100%,酶底比为5 U/20 m L时,大豆低聚糖的水解率为96.86%,重复使用5次后大豆低聚糖的水解率为59.70%;壳聚糖固定化酶的最适p H为4.0,温度为60℃,保存31 d后相对酶活为(58.85±0.00058)%,水解8.0 h后大豆低聚糖的水解率达到100%,酶底比为5 U/20 m L时,大豆低聚糖的水解率为97.93%,重复使用5次后大豆低聚糖的水解率为99.33%。与游离酶相比,固定化后的α-半乳糖苷酶展现了良好的稳定性和重复使用效果。

α-galactosidase is a key enzyme which can solve the problem of food intolerance of soybean products. The activity of microbial α-galactosidase is not high and it has low thermal resistance. In this paper, sodium alginate and chitosan immobilization carriers were used to immobilize α-galactosidase from Aspergillus oryzae. The optimum pH and temperature of the immobilized enzyme, the optimal enzyme ratio for hydrolysis of soybean oligosaccharides, and its reuse and storage conditions were studied. The experimental results showed that the optimum pH of free enzyme was 4.0, its optimum temperature was 50 ℃ and the hydrolysis rate of soybean oligosaccharides in soymilk was 79.28% after 8.0 hours. The optimum pH of the alginate immobilized enzyme was 7.0, the optimum temperature was45 ℃, the relative enzyme activity was （88.10±0.0029）% after 52 days of storage. The hydrolysis rate of soybean oligosaccharide in soymilk reached 80% after hydrolysis for 8.0 hours. When the ratio was 5 U/20 mL, the hydrolysis rate of soybean oligosaccharides was 96.86%, and the hydrolysis rate of soybean oligosaccharides was 59.70% after 5 times of repeated use. The optimum pH of chitosan immobilized enzyme was 4.0 and its optimum temperature was 60 ℃. After 31 days of storage, the relative enzyme activity was （58.85±0.00058）%. The hydrolysis rate of soybean oligosaccharides in soymilk reached 80% after hydrolysis for 8.0 hours. The hydrolysis rate of soybean oligosaccharides was 97.93% when the enzyme base ratio was 5 U/20 mL. The hydrolysis rate of soybean oligosaccharides after 5 repeated uses was 99.33%. Thus, the immobilized α-galactosidase in this study exhibited good stability, hydrolysis of soybean oligosaccharides and reusability.