State Key Laboratory of Microbial Technology, Shandong University, Qingdao, China.
Shandong Academy of Chinese Medicine, Jinan, 250014, China.
Bioprocess Biosyst Eng. 2021 Jun;44(6):1021-1032. doi: 10.1007/s00449-020-02505-3. Epub 2021 Jan 22.
L-Xylulose is a rare ketopentose which inhibits α-glucosidase and is an indicator of hepatitis or liver cirrhosis. This pentose is also a precursor of other rare sugars such as L-xylose, L-ribose or L-lyxose. Recombinant E. coli expressing xylitol-4-dehydrogenase gene of Pantoea ananatis was constructed. A cost-effective culture media were used for L-xylulose production using the recombinant E. coli strain constructed. Response surface methodology was used to optimize these media components for L-xylulose production. A high conversion rate of 96.5% was achieved under an optimized pH and temperature using 20 g/L xylitol, which is the highest among the reports. The recombinant E. coli cells expressing the xdh gene were immobilized in calcium alginate to improve recycling of cells. Effective immobilization was achieved with 2% (w/v) sodium alginate and 3% (w/v) calcium chloride. The immobilized E. coli cells retained good stability and enzyme activity for 9 batches with conversion between 53 and 92% which would be beneficial for economical production of L-xylulose.
L-木酮糖是一种罕见的酮戊糖，可抑制α-葡萄糖苷酶，是肝炎或肝硬化的标志物。这种戊糖也是其他稀有糖如 L-木糖、L-阿拉伯糖或 L-苏糖的前体。构建了表达泛菌属木糖-4-脱氢酶基因的重组大肠杆菌。使用构建的重组大肠杆菌菌株，使用具有成本效益的培养基生产 L-木酮糖。使用响应面法优化这些培养基成分以生产 L-木酮糖。在优化的 pH 值和温度下，使用 20g/L 木糖醇可实现高达 96.5%的高转化率，这在报道中是最高的。表达 xdh 基因的重组大肠杆菌细胞被固定在海藻酸钠中，以提高细胞的回收利用率。使用 2%（w/v）海藻酸钠和 3%（w/v）氯化钙可实现有效的固定化。固定化的大肠杆菌细胞保留了良好的稳定性和酶活性，可进行 9 批转化，转化率在 53%至 92%之间，这将有利于 L-木酮糖的经济生产。
