1,3-Propanediol (1,3-PDO) is an important synthetic monomer for the production of polytrimethylene terephthalate (PTT). Here, we engineered Klebsiella pneumoniae by a multi-strategy to improve 1,3-PDO production and reduce by-products synthesis. First, the 2,3-butanediol (2,3-BDO) synthesis pathway was blocked by deleting the budB gene, resulting in a 74% decrease of 2,3-BDO titer. The synthesis of lactate was decreased by 79% via deleting the ldhA gene, leading to a 10% increase of 1,3-PDO titer. Further, reducing ethanol synthesis by deleting the aldA gene led to a 64% decrease of ethanol titer, and the 1,3-PDO titer and yield on glycerol increased by 12 and 10%, respectively. Strengthening the TCA cycle by overexpressing the mdh gene improved 1,3-PDO synthesis effectively. Under 5-L fed-batch fermentation conditions, compared to wild type strain, the production of 2,3-BDO, lactate and ethanol in the mutant strain decreased by 73, 65 and 50%, respectively. Finally, the production of 1,3-PDO was 73.5 g/L with a molar yield of 0.67 mol/mol glycerol, improved 16% and 20%, respectively. This work provides a combined strategy for improving 1,3-PDO production by strengthening the TCA cycle to relieve metabolic stress by deleting genes of by-products synthesis, which was also beneficial for the extraction and separation of downstream products.

中文翻译：

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由于阻断肺炎克雷伯菌的副产物合成途径，加强三氯乙酸循环以减轻代谢压力。

1,3-丙二醇 (1,3-PDO) 是生产聚对苯二甲酸丙二醇酯 (PTT) 的重要合成单体。在这里，我们通过多策略改造肺炎克雷伯菌，以提高 1,3-PDO 产量并减少副产物合成。首先，通过删除budB基因来阻断 2,3-丁二醇 (2,3-BDO) 合成途径，导致 2,3-BDO 滴度下降 74%。通过删除ldhA基因，乳酸的合成减少了 79% ，导致 1,3-PDO 滴度增加了 10%。此外，通过删除aldA基因减少乙醇合成导致乙醇滴度降低 64%，1,3-PDO 滴度和甘油产量分别增加 12% 和 10%。通过过度表达 TCA 循环来加强mdh基因有效地改善了 1,3-PDO 的合成。在 5-L 分批补料发酵条件下，与野生型菌株相比，突变菌株中 2,3-BDO、乳酸和乙醇的产量分别下降了 73%、65% 和 50%。最后，1,3-PDO 的产量为 73.5 g/L，摩尔收率为 0.67 mol/mol 甘油，分别提高了 16% 和 20%。这项工作提供了一种通过加强TCA循环以通过删除副产物合成基因来缓解代谢压力来提高1,3-PDO产量的组合策略，这也有利于下游产物的提取和分离。