中文摘要：

产紫青霉菌株（Penicillium purpurogenum Li-3）能定向转化甘草酸（GL）为单葡萄糖醛酸基甘草次酸（glycyrrtinic acid 3-O-mono-β-D-glucuronide,GAMG）,针对课题组前期海藻酸钙包埋产紫青霉Li-3的珠体机械强度不高,操作使用性能低等问题,通过添加天然物质和化学处理改变凝胶结构,提高改性海藻酸钙珠体的机械强度,并考察了改性海藻酸钙固定化细胞的催化性质。利用改性海藻酸钙固定的产紫青霉（Penicillium purpurogenum Li-3）微球在具有隔离筛的改进型填充床反应器中连续转化甘草酸（GL）生产单葡萄糖醛酸基甘草次酸（GAMG）。结果表明添加4%的硅藻土能够改善固定化细胞微球的机械强度,提高了反应的转化率。改性前后的固定化细胞微球的最适p H值和最适温度均未发生变化,但改性的固定化细胞反应转化率与对照相比分别提高了22%和30%。向底物中添加0.12%的吐温-80能进一步使GAMG的产量提高44%。同时,改性的固定化细胞微球具有较好的贮存稳定性和重复使用性。最后利用改性固定化细胞微球在具有隔离筛的改进型填充床反应器内实现了连续生产GAMG,在最佳反应条件下,GAMG的产量为0.193 g/（L·d）,GL的转化率为34%,时空产率约为13.7μmol/（L·h）。利用改性固定化细胞微球在改进型的填充床反应器内进行连续反应生产GAMG,为建立高效全细胞转化甘草酸合成GAMG的反应体系奠定了基础。

英文摘要：

Microbial immobilization is widely used in many areas such as bioengineering, biochemical separation and analysis. Glycyrrhizin（GL） can be transformed into glycyrrtinic acid 3-O-mono-β-D-glucuronide（GAMG） by Penicillium purpurogenum Li-3 screened in the previous study. Penicillium purpurogenum Li-3 cells were immobilized into calcium alginate beads for GAMG production. However, the low mechanical strength and thus poor utilizable properties of the calcium lginate beads limited their applications. The mechanical strength of calcium alginate beads was improved by adding natural substances as well as chemical treating. Subsequently, the catalytic activities of the modified calcium alginate immobilized cells were characterized. At last, the continuous production of GAMG by modified immobilized cells in a self- designed packed bed reactor was further investigated. The obtained results were as follows： Firstly,diatomite was confirmed to be useful for improving the mechanical strength of calcium alginate beads with an optimal concentration of 4%. The so obtained modified immobilized cells were reused for 23 times in shake flask experiments.Subsequently, the modified immobilized cells were employed for GAMG production. After 48 h reaction, the output of GAMG was up to 1.62 g/L and the conversion of GL was 54%. The cost of the added diatomite was relatively low so that it can be used for further large-scale production. Secondly, the effects of p H, temperature and synergistic agent Tween-80 on the conversion efficiency and storage stability of the modified immobilized cells were studied. The results showed that the modification of immobilized cells made no difference on their p H and temperature, which were 5.4 and 35 ℃,respectively. However, the enzyme activity was enhanced compared with the original immobilized cells. In detail, the conversion efficiency of GL by the modified immobilized cells was improved when 0.12% Tween-80 was added into the substrates, leading to the increase of GAMG output by 44% compa