β-呋喃果糖苷酶的生产及对甜菊苷和莱鲍迪A苷的酶法改性研究

Production of β-fructofuranosidase and Optimization of Enzymatic Modification Process for Stevioside and Rebaudioside A

用Arthrobacter sp.10137生产一种β-呋喃果糖苷酶(FFase),SDS-PAGE检测纯化后的酶分子质量为48.7ku左右,酶的比活力为19.81U/mg。纯酶的最适pH值和温度分别为6.5和40℃,并在pH6～8及40℃以下稳定。纯酶对甜菊苷和莱鲍迪A苷改性的最适条件是:酶量为15U/mL,莱鲍迪A苷和甜菊苷与蔗糖的摩尔比分别为0.0005:1和0.0012:1,反应时间为15h。在最适条件下,莱鲍迪A苷和甜菊苷的最大转化率分别为69.4%和72.0%。

A β-fructofuranosidase from Arthrobacter sp. 10137 was produced and purified to electrophoretic homogeneity with the molecular mass of 48.7 ku on SDS--PAGE, of which have 19.81 U/rag of specific activity. The optimum pH and temperature of the purified enzyme were 6.5 and 40 ℃ respectively and it was stable in the pH range of 6-8 and below the temperature of 40 ℃. The purified enzyme was used to modify the structure of stevioside and rebaudioside A. The reaction conditions were optimized as 15 U/mL of enzyme amount, 0.000 5 ： 1 and 0.001 2 ： 1 of molecular ratio of RA and St to sucrose, reaction time of 15 h. The maximal conversion ratio of RA and St were 69.4 % and 72.0 % respectix;ely under the above optimal conditions.