L-Threonine is an important branched-chain amino acid and could be applied in feed, drugs, and food. In this study, L-threonine production in an L-threonine-producing Escherichia coli strain TWF001 was significantly increased by overexpressing the gene cluster phaCAB from Ralstonia eutropha. TWF001/pFW01-phaCAB could produce 96.4-g/L L-threonine in 3-L fermenter and 133.5-g/L L-threonine in 10-L fermenter, respectively. In addition, TWF001/pFW01-phaCAB produced 216% more acetyl-CoA, 43% more malate, and much less acetate than the vector control TWF001/pFW01, and meanwhile, TWF001/pFW01-phaCAB produced poly-3-hydroxybutyrate, while TWF001/pFW01 did not. Transcription analysis showed that the key genes in the L-threonine biosynthetic pathway were up-regulated, the genes relevant to the acetate formation were down-regulated, and the gene acs encoding the enzyme which converts acetate to acetyl-CoA was up-regulated. The results suggested that overexpression of the gene cluster phaCAB in E. coli benefits the enhancement of L-threonine production.

中文翻译：

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通过过表达基因簇phaCAB来增加大肠杆菌中L-苏氨酸的产量。

L-苏氨酸是一种重要的支链氨基酸，可用于饲料，药品和食品中。在这项研究中，通过过量表达富营养小球藻（Ralstonia eutropha）的基因簇phaCAB，可显着提高生产L-苏氨酸的大肠杆菌TWF001中L-苏氨酸的产量。TWF001 / pFW01-phaCAB在3-L发酵罐中可分别生产96.4-g / L L-苏氨酸，在10-L发酵罐中可生产133.5-g / L L-苏氨酸。此外，与载体对照TWF001 / pFW01相比，TWF001 / pFW01-phaCAB产生的乙酰辅酶A含量高216％，苹果酸含量高43％，乙酸盐含量低得多，同时，TWF001 / pFW01-phaCAB产生聚-3-羟基丁酸酯，而TWF001 / pFW01没有。转录分析表明，L-苏氨酸生物合成途径中的关键基因被上调，与乙酸盐形成相关的基因被下调，编码将乙酸酯转化为乙酰辅酶A的酶的基因acs被上调。结果表明，在大肠杆菌中基因簇phaCAB的过表达有利于L-苏氨酸的产生。