Abstract Baicalin-β-D-glucuronidase was produced from a culture of Aspergillus niger b.48 strain using Scutellaria root extract as an enzyme inducer, purified and characterized. The enzyme’s molecular weight was approximately 45 kDa; its optimal operating temperature and pH were 50 °C and 5.0, respectively. The enzyme specifically hydrolysed 7-O-β-D-glucuronide of baicalin into baicalein, weakly hydrolysed β-D-glucuronide of p-nitrophenyl-β-D-glucuronide and p-phenolphthalein-β-D-glucuronide, but did not hydrolyse β-D-glucuronide of glycyrrhizin. The Michaelis constant (Km) was 21.74 mM; Vmax was 11.63 mM/h. Common metallic ions almost did not effect enzyme activity; greater than 10 mM/L Cu2+ and greater 50 mM/L Fe3+ ion strongly inhibited enzyme activity. The use of pure enzyme in baicalin conversion to baicalein was costly, the crude baicalin-β-D-glucuronidase from A. niger b.48 strain was used in the preparation of baicalein from baicalin to keep costs low. The optimum conditions for baicalein production from crude enzyme reaction were 1% baicalin reacting for 20 h to 24 h at pH 5.0 and 50 °C. Here, 10.7 g baicalein was obtained from 20 g baicalin using the crude enzyme, and the molar yield was 88.4%. Therefore, active baicalein was successfully produced at low cost from baicalin using a non-transgenic crude enzyme from A. niger b.48.

中文翻译：

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使用来自黑曲霉 b.48 菌株的黄芩苷-β-D-葡萄糖醛酸酶从黄芩苷制备黄芩素

摘要 以黄芩根提取物为酶诱导剂，从黑曲霉b.48菌株培养物中制备黄芩苷-β-D-葡萄糖醛酸酶，并对其进行纯化和表征。该酶的分子量约为 45 kDa；其最佳操作温度和 pH 值分别为 50 °C 和 5.0。该酶将黄芩苷的7-O-β-D-葡萄糖苷酸特异性水解为黄芩素，弱水解对硝基苯基-β-D-葡萄糖苷酸的β-D-葡萄糖苷酸和对酚酞-β-D-葡萄糖苷酸，但不水解甘草甜素的β-D-葡萄糖醛酸苷。米氏常数 (Km) 为 21.74 mM；Vmax 为 11.63 mM/h。普通金属离子几乎不影响酶活性；大于 10 mM/L Cu2+ 和大于 50 mM/L Fe3+ 离子强烈抑制酶活性。使用纯酶将黄芩素转化为黄芩素成本高昂，采用黑曲霉b.48菌株黄芩苷-β-D-葡萄糖醛酸苷酶粗品制备黄芩苷，成本低廉。粗酶反应生产黄芩素的最佳条件为1%黄芩苷在pH 5.0、50℃反应20-24小时。这里，使用粗酶从20g黄芩苷中得到10.7g黄芩素，摩尔收率为88.4%。因此，使用来自黑曲霉b.48的非转基因粗酶从黄芩苷中成功地以低成本生产活性黄芩素。摩尔收率为88.4%。因此，使用来自黑曲霉b.48的非转基因粗酶从黄芩苷中成功地以低成本生产活性黄芩素。摩尔收率为88.4%。因此，使用来自黑曲霉b.48的非转基因粗酶从黄芩苷中成功地以低成本生产活性黄芩素。