肺炎克雷伯菌可利用葡萄糖或甘油作为碳源生产1,3-丙二醇或2,3-丁二醇,分别。在肺炎克雷伯菌的代谢中,氢化酶-3负责从甲酸中生产H2,但它与1,3-丙二醇和2,3-丁二醇的合成途径没有直接关系。在本研究的第一部分,hycefg,编码氢化酶-3亚基的基因被敲除,因此,肺炎克雷伯氏菌ΔhycEFG在使用甘油作为碳源的培养过程中失去了产生H2的能力。因此,1,3-丙二醇的浓度增加,底物(甘油)转化率达到0.587mol/mol。然后,构建肺炎克雷伯菌ΔldhAΔhycEFG以消除乳酸合成,从而导致1,3-丙二醇浓度进一步增加。在间歇条件下底物(甘油)转化率为0.628mol/mol,与野生型菌株(0.545mol/mol)相比更高。此外,由于adhE编码一种催化乙醛生产乙醇的醇脱氢酶,构建肺炎克雷伯菌ΔldhAΔadhEΔhycEFG以防止乙醇产生。与预期相反,这并没有导致进一步的增长,而是减少了1,3-丙二醇的产量。在本研究的第二部分,使用葡萄糖作为碳源以产生2,3-丁二醇。敲除hycEFG对2,3-丁二醇的产生具有明显的积极作用。特别是在肺炎克雷伯菌ΔldhAΔadhEΔhycEFG中,底物(葡萄糖)转化率达到0.730mol/mol,与野生型菌株(0.504mol/mol)相比更高。这项工作表明,氢化酶-3的失活可能对肺炎克雷伯菌的代谢调节具有整体作用,导致两种重要的工业散装化学品的产量提高,1,3-丙二醇和2,3-丁二醇。
Klebsiella pneumoniae can use glucose or glycerol as carbon sources to produce 1,3-propanediol or 2,3-butanediol, respectively. In the metabolism of Klebsiella pneumoniae, hydrogenase-3 is responsible for H2 production from formic acid, but it is not directly related to the synthesis pathways for 1,3-propanediol and 2,3-butanediol. In the first part of this research, hycEFG, which encodes subunits of the enzyme hydrogenase-3, was knocked out, so K. pneumoniae ΔhycEFG lost the ability to produce H2 during cultivation using glycerol as a carbon source. As a consequence, the concentration of 1,3-propanediol increased and the substrate (glycerol) conversion ratio reached 0.587 mol/mol. Then, K. pneumoniae ΔldhAΔhycEFG was constructed to erase lactic acid synthesis which led to the further increase of 1,3-propanediol concentration. A substrate (glycerol) conversion ratio of 0.628 mol/mol in batch conditions was achieved, which was higher compared to the wild type strain (0.545 mol/mol). Furthermore, since adhE encodes an alcohol dehydrogenase that catalyzes ethanol production from acetaldehyde, K. pneumoniae ΔldhAΔadhEΔhycEFG was constructed to prevent ethanol production. Contrary to expectations, this did not lead to a further increase, but to a decrease in 1,3-propanediol production. In the second part of this research, glucose was used as the carbon source to produce 2,3-butanediol. Knocking out hycEFG had distinct positive effect on 2,3-butanediol production. Especially in K. pneumoniae ΔldhAΔadhEΔhycEFG, a substrate (glucose) conversion ratio of 0.730 mol/mol was reached, which is higher compared to wild type strain (0.504 mol/mol). This work suggests that the inactivation of hydrogenase-3 may have a global effect on the metabolic regulation of K. pneumoniae, leading to the improvement of the production of two industrially important bulk chemicals, 1,3-propanediol and 2,3-butanediol.