An extracellular fructosyltransferase (Ftase) enzyme with a molar mass of ≈70 kDa from a newly isolated indigenous coprophilous fungus Aspergillus niger sp. XOBP48 is purified to homogeneity and characterized in this study. The enzyme was purified to 4.66-fold with a total yield of 15.53% and specific activity of 1219.17 U mg⁻¹ of protein after a three-step procedure involving (NH₄)₂SO₄ fractionation, dialysis and anion exchange chromatography. Ftase showed optimum activity at pH 6.0 and temperature 50 °C. Ftase exhibited over 80% residual activity at pH range of 4.0–10.0 and ≈90% residual activity at temperature range of 40–60 °C for 6 h. Metal ion inhibitors Hg²⁺ and Ag⁺ significantly inhibited Ftase activity at 1 mmol concentration. Ftase showed K_m, v_max and k_cat values of 79.51 mmol, 45.04 µmol min⁻¹ and 31.5 min⁻¹, respectively, with a catalytic efficiency (k_cat/K_m) of 396 µmol⁻¹ min⁻¹ for the substrate sucrose. HPLC-RI experiments identified the end products of fructosyltransferase activity as monomeric glucose, 1-kestose (GF₂), and 1,1-kestotetraose (GF₃). This study evaluates the feasibility of using this purified extracellular Ftase for the enzymatic synthesis of biofunctional fructooligosaccharides.

一种胞外果糖基转移酶 (Ftase)，摩尔质量约为 70 kDa，来自新分离的本土粪菌黑曲霉(Aspergillus niger sp)。 XOBP48 在本研究中被纯化至均质并进行表征。经过(NH ₄ ) ₂ SO ₄分级、透析、阴离子交换层析三步，酶纯化率达到4.66倍，总收率为15.53%，蛋白比活为1219.17 U mg ^{-1 。} Ftase 在 pH 6.0 和温度 50 °C 时表现出最佳活性。 Ftase 在 pH 值 4.0–10.0 范围内表现出超过 80% 的残余活性，在 40–60 °C 温度范围内 6 小时表现出约 90% 的残余活性。金属离子抑制剂Hg ²⁺和Ag ⁺在1 mmol浓度下显着抑制Ftase活性。 Ftase 显示K _m 、 v _max和k _cat值分别为 79.51 mmol、45.04 µmol min ^-1和 31.5 min ^-1 ，底物的催化效率 ( k _cat / K _m ) 为 396 µmol ^-1 min ^-1蔗糖。 HPLC-RI 实验鉴定出果糖基转移酶活性的终产物为单体葡萄糖、1-酮糖 (GF ₂ ) 和 1,1-酮四糖 (GF ₃ )。本研究评估了使用这种纯化的细胞外 Ftase 酶法合成生物功能低聚果糖的可行性。