School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
School of Biochemical Engineering, Pontificia Universidad Católica de Valparaíso, Avenida Brasil 2147, Valparaíso, Chile.
Bioresour Technol. 2015 Aug;190:122-31. doi: 10.1016/j.biortech.2015.04.039. Epub 2015 Apr 22.
Synthesis of lactulose under repeated-batch operation was done with cross-linked aggregates of Aspergillus oryzae β-galactosidase (CLAGs). The effect of the crosslinking agent to enzyme mass ratio and cross-linking time were first evaluated. Best results were obtained at 5.5gdeglutaraldehyde/g enzyme at 5h of cross-linking, obtaining a specific activity of 15,000IUg(-1), with 30% immobilization yield. CLAG was more stable than the free enzyme under non-reactive conditions with a half-life of 123h at 50°C and when operated in repeated-batch mode, yield and productivity was 3.8 and 4.3 times higher. Maximum number of batches was determined considering biocatalyst replacement at 50% residual activity. 98 and 27 batches could be performed under such criterion at fructose/lactose molar ratio of 4 and 20 respectively, reflecting that enzyme stability is strongly affected by the sugars distribution in the reaction medium.
采用米曲霉β-半乳糖苷酶交联聚集体（CLAG）进行乳果糖的分批补料合成。首先考察了交联剂与酶质量比和交联时间的影响。在交联 5h 时，戊二醛与酶的质量比为 5.5g/deg，得到的比酶活为 15000IU/g，固定化酶的收率为 30%。CLAG 在非反应条件下比游离酶更稳定，在 50°C 下半衰期为 123h，在分批补料操作中，产率和生产力分别提高了 3.8 倍和 4.3 倍。考虑到生物催化剂的残余活性为 50%时进行更换，确定了最大批次数。在果糖/乳糖摩尔比分别为 4 和 20 时，可以在此标准下进行 98 和 27 批反应，这表明酶的稳定性受到反应介质中糖分布的强烈影响。
