Abstract：
As the highest-demand vitamin, the development of a one-step vitamin C synthesis process has been slow for a long time. In previous research, a Gluconobacter oxydans strain (GKLG9) was constructed that can directly synthesize 2-keto-L-gulonic acid (2-KLG) from glucose, but carbon source utilization remained low. Therefore, this study first identified the gene 4kas (4-keto-D-arabate synthase) to reduce the loss of extracellular carbon and inhibit the browning of fermentation broth. Then, promoter engineering was conducted to enhance the intracellular glucose transport pathway and concentrate intracellular glucose metabolism on the pentose phosphate pathway to provide more reducing power. Finally, by introducing the D-sorbitol pathway, the titer of 2-KLG was increased to 38.6 g/L within 60 h in a 5-L bioreactor, with a glucose-to-2-KLG conversion rate of about 46 %. This study is an important step in the development of single-bacterial one-step fermentation to produce 2-KLG.
摘要：
作为需求量最大的维生素，一步维生素C合成过程的发展一直很缓慢。在以前的研究中，构建了一个氧化葡糖杆菌菌株（GKLG9），可以从葡萄糖直接合成2-酮-L-古洛糖酸（2-KLG），但是碳源利用率仍然很低。因此,这项研究首次确定了基因4kas（4-酮-D-阿拉伯糖酸合酶），以减少细胞外碳的损失并抑制发酵液的褐变。然后，进行启动子工程以增强细胞内葡萄糖转运途径，并将细胞内葡萄糖代谢集中在磷酸戊糖途径上，以提供更多的还原能力。最后,通过引入D-山梨醇途径，在5-L生物反应器中，2-KLG的滴度在60小时内增加到38.6g/L，葡萄糖到2-KLG的转化率约为46%。这项研究是发展单细菌一步发酵生产2-KLG的重要步骤。
