2,3-Dihydroxyisovalerate is an intermediate of valine and leucine biosynthesis pathway; however, no natural microorganism has been found yet that can accumulate this compound. Klebsiella pneumoniae is a useful bacterium that can be used as a workhorse for the production of a range of industrially desirable chemicals. Dihydroxy acid dehydratase, encoded by the ilvD gene, catalyzes the reaction of 2-ketoisovalerate formation from 2,3-dihydroxyisovalerate. In this study, an ilvD disrupted strain was constructed which resulted in the inability to synthesize 2-ketoisovalerate, yet accumulate 2,3-dihydroxyisovalerate in its culture broth. 2,3-Butanediol is the main metabolite of K. pneumoniae and its synthesis pathway and the branched-chain amino acid synthesis pathway share the same step of the α-acetolactate synthesis. By knocking out the budA gene, carbon flow into the branched-chain amino acid synthesis pathway was upregulated, which resulted in a distinct increase in 2,3-dihydroxyisovalerate levels. Lactic acid was identified as a by-product of the process and by blocking the lactic acid synthesis pathway, a further increase in 2,3-dihydroxyisovalerate levels was obtained. The culture parameters of 2,3-dihydroxyisovalerate fermentation were optimized, which include acidic pH and medium level oxygen supplementation to favor 2,3-dihydroxyisovalerate synthesis. At optimal conditions (pH 6.5, 400 rpm), 36.5 g/L of 2,3-dihydroxyisovalerate was produced in fed-batch fermentation over 45 h, with a conversion ratio of 0.49 mol/mol glucose. Thus, a biological route of 2,3-dihydroxyisovalerate production with high conversion ratio and final titer was developed, providing a basis for an industrial process.

2,3-二羟基异戊酸酯是缬氨酸和亮氨酸生物合成途径的中间体；然而，尚未发现可以积累该化合物的天然微生物。肺炎克雷伯氏菌是有用的细菌，可用作生产一系列工业上所需的化学品的主力军。由ilvD基因编码的二羟基酸脱水酶催化由2，3-二羟基异戊酸酯形成2-酮异戊酸酯的反应。在该研究中，构建了ilvD破坏菌株，该菌株导致无法合成2-酮异戊酸，但在其培养液中积累了2,3-二羟基异戊酸。2,3-丁二醇是肺炎克雷伯菌的主要代谢产物它的合成途径和支链氨基酸合成途径都与α-乙酰乳酸合成步骤相同。通过剔除芽在基因中，进入支链氨基酸合成途径的碳流量被上调，这导致2,3-二羟基异戊酸酯水平明显增加。乳酸被鉴定为该过程的副产物，并且通过阻断乳酸合成途径，获得了2,3-二羟基异戊酸酯水平的进一步增加。优化了2,3-二羟基异戊酸酯发酵的培养参数，包括酸性pH值和中等水平的氧气补充以促进2,3-二羟基异戊酸酯的合成。在最佳条件下（pH 6.5，400 rpm），分批补料发酵历时45 h产生了36.5 g / L的2,3-二羟基异戊酸，转化率为0.49 mol / mol葡萄糖。因此，开发了具有高转化率和最终效价的2,3-二羟基异戊酸生产生物学途径，